Optical disk, an optical disk barcode forming method, an optical disk reproduction apparatus, a marking forming apparatus, a method of forming a laser marking on an optical disk, and a method of manufacturing an optical disk

ABSTRACT

Disclosed is an optical disk barcode forming method wherein, as information to be barcoded, position information for piracy prevention, which is a form of ID, is coded as a barcode and is recorded by laser trimming on a reflective film in a PCA area of an optical disk. Then playing back the thus manufactured optical disk on a reproduction apparatus, the barcode data can be played back using the same optical pickup.

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to an optical disk, an optical diskbarcode forming method, an optical disk reproduction apparatus, amarking forming apparatus, a method of forming a laser marking on anoptical disk, and a method of manufacturing an optical disk.

[0003] 2. Related Art of the Invention

[0004] In the manufacturing process of optical disks, it has beencommonly practiced to record a serial number, lot number, etc. on eachoptical disk in the form of a barcode.

[0005] Since such information cannot be written to a pit informationarea of the optical disk, it has been practiced to write the barcodedinformation to a non-information area, or unused space, on the opticaldisk.

[0006] When reproducing (playing back) such an optical disk, the pitinformation is read by an optical pickup; to read the barcodedinformation such as a serial number, etc. recorded in thenon-information area, however, a separate reading device has been used.

[0007] In the above prior art optical disk, since information carrying aserial number and the like is not recorded in a pit area but recorded ina non-information area, as described above, a separate reading devicehas had to be provided in addition to the usual optical pickup, theresulting problem being increased complexity of the playback apparatusconstruction.

SUMMARY OF THE INVENTION

[0008] In view of the above problem with the prior art, it is an objectof the present invention to provide an optical disk wherein data such asa disk ID number, etc. is converted into a barcode and recorded in a pitarea in overwriting fashion, thereby permitting the use of a singleoptical pickup to read both the bit data and barcode data. It is anotherobject of the invention to provide a barcode forming method, etc. forsuch an optical disk.

[0009] The first invention is an optical disk on which data is recordedwith CLV, wherein, in a prescribed region of a pre-pit signal area onsaid disk, all or part of a barcode is written in overwriting fashion byselectively removing a reflective film in said prescribed region.

[0010] The second invention is an optical disk according to the firstinvention, wherein a control data area is provided for holding thereinphysical feature information concerning said optical disk, and anidentifier for indicating the presence or absence of said barcode isrecorded in said control data area.

[0011] The third invention is an optical disk according to the secondinvention, wherein a guard-band area where no data is recorded isprovided between said control data area and said prescribed region ofsaid pre-pit signal area.

[0012] The 4th invention is an optical disk according to the firstinvention, wherein said barcode is formed in such a manner that two ormore barcode signals cannot occur within one prescribed time slot.

[0013] The 5th invention is an optical disk according to the firstinvention, wherein said barcode contains data at least including IDinformation uniquely given to said optical disk.

[0014] The 6th invention is an optical disk according to the 5thinvention, wherein said barcode contains data including, in addition tosaid ID information, a public key of a public key encryption functioncorresponding to said ID information, said public key being used whenencrypting prescribed data for transmission to an external party inorder to obtain from said external party a password required toreproduce said optical disk.

[0015] The 7th invention is an optical disk according to the 5thinvention, wherein said ID information is encrypted or applied a digitalsignature to.

[0016] The 8th invention is an optical disk according to the 7thinvention, wherein a secret key of a public key encryption function isused when applying encryption or a digital signature to said IDinformation.

[0017] The 9th invention is an optical disk according to any one ofinventions from first to 8th, wherein said optical disk is constructedfrom two disk-substrates laminated together.

[0018] The 10th invention is an optical disk barcode forming methodwherein pulsed laser light from a light source is made into arectangular beam pattern by using a rectangular mask and saidrectangular beam pattern is focused on a reflective film in a pre-pitsignal region in a prescribed radius portion of an optical disk on whichdata is recorded, and at the same time, said optical disk is rotated,thereby forming a plurality of rectangular reflective-film removedregions as a barcode in the same radius portion on said reflective film.

[0019] The 11th invention is an optical disk barcode forming methodaccording to the 10th invention, wherein said optical disk includes acontrol data area for holding therein physical feature informationconcerning said optical disk, and an identifier for indicating thepresence or absence of said barcode is recorded in said control dataarea.

[0020] The 12th invention is an optical disk barcode forming methodaccording to the 11th invention, wherein said barcode is formed in sucha manner that two or more barcode signals cannot occur within oneprescribed time slot.

[0021] The 13th invention is an optical disk barcode forming methodaccording to any one of inventions from 10th to 12th, wherein saidoptical disk is constructed from two disk-substrates laminated together.

[0022] The 14th invention is an optical disk reproduction apparatuswherein recorded contents of a main data recording area, recorded byforming pits on an optical disk, are reproduced by using a rotationalphase control for a motor, while recorded contents of a differentrecording area than said main data recording area, recorded byselectively forming low-reflectivity portions on a reflective film insaid different recording area, are reproduced by using rotational speedcontrol for said motor, and the recorded contents of said main datarecording area and the recorded contents of said different recordingarea are both reproduced by using the same optical pickup.

[0023] The 15th invention is an optical disk reproduction apparatusaccording to the 14th invention, wherein tracking control is notperformed in said different recording area.

[0024] The 16th invention is an optical disk reproduction apparatusaccording to the 14th invention, wherein tracking control is, in effect,performed in said different recording area.

[0025] The 17th invention is an optical disk reproduction apparatusaccording to the 16th invention, wherein said rotational speed is therotational speed that would be achieved in said different recording areaif said rotational phase control were applied.

[0026] The 18th invention is an optical disk reproduction apparatusaccording to the 14th invention, wherein the rotational speed of saidmotor in said rotational speed control is maintained at a prescribedvalue based on a result obtained by measuring a minimum length pit insaid different recording area.

[0027] The 19th invention is an optical disk reproduction apparatusaccording to the 14th invention, wherein said low-reflectivity portionsare a barcode formed by selectively removing said reflective film.

[0028] The 20th invention is an optical disk reproduction apparatusaccording to the 14th invention whererein

[0029] said low-reflectivity portions are a barcode, and

[0030] when reproducing the recorded contents of said differentrecording area, a high-frequency-component signal generated duringreproduction of said pits is reduced or eliminated by a low-pass filter,thereby making it possible to separate a signal which is reproduced fromsaid barcode.

[0031] The 21st invention is an optical disk reproduction apparatusaccording to the 14th invention, wherein

[0032] said low-reflectivity portions are a barcode, and

[0033] when reproducing the recorded contents of said differentrecording area, the width of a signal obtained by reading said barcodeis increased to a prescribed width and then measured with samplingpulses from a control section.

[0034] The 22nd invention is an optical disk reproduction apparatusaccording to any one of inventions from 14th to 21st, wherein saidoptical disk is constructed from two disk-substrates laminated together.

[0035] The 23rd invention is an optical disk reproduction apparatusaccording to the 14th invention, wherein said optical disk includes acontrol data area for holding therein physical feature informationconcerning said optical disk, and an identifier for indicating thepresence or absence of said barcode is recorded in said control dataarea.

[0036] The 24th invention is an optical disk reproduction apparatusaccording to claim 23, wherein, after reading recorded contents of saidcontrol data area and judging the presence or absence of said barcode,it is determined whether an optical pickup should be moved to an innerportion or an outer portion of said optical disk.

[0037] The 25th invention is a marking forming apparatus whichcomprises:

[0038] marking forming means for applying a marking on a reflective filmformed on a disk;

[0039] marking position detecting means for detecting a position of saidmarking; and

[0040] position information writing means for converting at least saiddetected position information or information concerning said positioninformation into a barcode, and for selectively removing said reflectivefilm to write said barcode to an optical disk on which data is recordedwith CLV,

[0041] wherein all or part of said barcode is written in overwritingfashion to a prescribed region of a pre-pit signal area on said opticaldisk.

[0042] The 26th invention is a marking forming apparatus according tothe 25th invention, wherein said disk is constructed from twodisk-substrates laminated together.

[0043] The 27th invention is a marking forming means according to the25th invention, wherein said position information writing means includesencrypting means for encrypting at least said detected positioninformation or information concerning said position information, andwrites contents thus encrypted to said disk.

[0044] The 28th invention is a marking forming apparatus according tothe 25th invention, wherein said position information writing meansincludes digital signature means for applying a digital signature to atleast said detected position information or information concerning saidposition information,

[0045] and the writing at least said detected position information orinformation concerning said position information means writinginformation concerning a result of said digital signature application tosaid disk.

[0046] The 29th invention is a reproduction apparatus which comprises:

[0047] position information reading means for reading positioninformation of a marking or information concerning said positioninformation, said position information or said information being formedby (1) applying a marking on a reflective film formed on a disk, (2)detecting position of the marking, (3) converting detected said positioninformation or said information into a barcode and (4) writing thebarcode with selectively removing said reflective film on said opticaldisk on which data is recorded with CLV;

[0048] marking reading means for reading information concerning aphysical position of said marking;

[0049] comparing/judging means for performing comparison and judgementby using a result of reading by said position information reading meansand a result of reading by said marking reading means; and

[0050] reproducing means for reproducing data recorded on said opticaldisk in accordance with a result of the comparison and judgementperformed by said comparing/judging means,

[0051] wherein all or part of said barcode is written in overwritingfashion to a prescribed region of a pre-pit signal area on said opticaldisk.

[0052] The 30th invention is a reproduction apparatus according to the29th invention, wherein at least said detected position information orinformation concerning said position information is written to said diskby position information writing means.

[0053] The 31st invention is a reproduction apparatus according to the30th invention, wherein

[0054] said position information writing means includes encrypting meansfor encrypting at least said detected position information orinformation concerning said position information, and

[0055] said position information reading means includes decrypting meanscorresponding to said encrypting means, and by using said decryptingmeans, decrypts said encrypted position information or informationconcerning said position information.

[0056] The 32nd invention is a reproduction apparatus according to the30th invention, wherein

[0057] said position information writing means includes digitalsignature means for applying a digital signature to at least saiddetected position information or information concerning said positioninformation, and writes information concerning a result of said digitalsignature application to said disk,

[0058] and said position information reading means includes

[0059] authenticating means corresponding to said digital signaturemeans, and

[0060] position information extracting means for obtaining said positioninformation from an authentication process performed by saidauthenticating means and/or from said information concerning the resultof said digital signature application,

[0061] when an output indicating correctness of said authenticationresult is produced from said authenticating means, saidcomparing/judging means performs the comparison and judgement by usingthe position information obtained by said position informationextracting means and the result of reading by said marking readingmeans, and when said output indicating correctness is not produced, thereproduction is not performed.

[0062] The 33rd invention is a method of manufacturing a disk, whichcomprises the steps of:

[0063] forming at least one disk;

[0064] forming a reflective film to said formed disk;

[0065] applying at least one marking to said reflective film;

[0066] detecting at least one position of said marking; and

[0067] encrypting said detected position information and writing saidencrypted information onto said disk,

[0068] wherein, when encrypting and writing, at least said encryptedinformation is converted into a barcode, and said barcode is written byselectively removing said reflective film on said disk on which data isrecorded with CLV, all or part of said barcode being written inoverwriting fashion to a prescribed region of a pre-pit signal area onsaid disk.

[0069] The 34th invention is a method of manufacturing a disk, whichcomprises the steps of:

[0070] forming at least one disk;

[0071] forming a reflective film to said formed disk;

[0072] applying at least one marking to said reflective film;

[0073] detecting at least one position of said marking; and

[0074] applying a digital signature to said detected positioninformation and writing onto said disk,

[0075] wherein, when applying said digital signature and writing, atleast a result of said digital signature is converted into a barcode,and said barcode is written by selectively removing said reflective filmon said disk on which data is recorded with CLV, all or part of saidbarcode being written in overwriting fashion to a prescribed region of apre-pit signal area on said disk.

[0076] The 35th invention is a disk wherein a marking is formed by alaser to a reflective film of said disk holding data written thereon, atleast position information of said marking or information concerningsaid position information is encrypted or applied a digital signature,at least said encrypted information or digital signature-appendedinformation is converted into a barcode, and said barcode is written byselectively removing said reflective film on said disk on which data isrecorded with CLV, all or part of said barcode being written inoverwriting fashion to a prescribed region of a pre-pit signal area onsaid disk.

BRIEF DESCRIPTION OF THE DRAWINGS

[0077]FIG. 1 is a diagram showing a disk manufacturing process and asecondary recording process according to the present embodiment;

[0078]FIG. 2(a) is a top plan view of a disk according to theembodiment, (b) is a top plan view of the disk according to theembodiment, (c) is a top plan view of the disk according to theembodiment, (d) is a transverse sectional view of the disk according tothe embodiment, and (e) is a waveform diagram of a reproduced signalaccording to the embodiment;

[0079]FIG. 3 is a flowchart illustrating a process of recordingencrypted position information on a disk in the form of a barcodeaccording to the present embodiment;

[0080]FIG. 4 is a diagram showing a disk fabrication process and asecondary recording process (part 1) according to the presentembodiment;

[0081]FIG. 5 is a diagram showing the disk fabrication process and thesecondary recording process (part 2) according to the presentembodiment;

[0082]FIG. 6 is a diagram showing a two-layer disk fabrication process(part 1) according to the present embodiment;

[0083]FIG. 7 is a diagram showing the two-layer disk fabrication process(part 2) according to the present embodiment;

[0084]FIG. 8(a) is an enlarged view of a nonreflective portion of alaminated type according to the present embodiment, and (b) is anenlarged view of a nonreflective portion of a single-plate typeaccording to the present embodiment;

[0085]FIG. 9(a) is a reproduced-waveform diagram for a nonreflectiveportion according to the present embodiment, (b) is areproduced-waveform diagram for a nonreflective portion according to thepresent embodiment, (c) is a reproduced-waveform diagram for anonreflective portion according to the present embodiment, and (d) is aplan view of a master disk produced by a master disk method;

[0086]FIG. 10(a) is a cross-sectional view of a nonreflective portion ofthe laminated type according to the present embodiment, and (b) is across-sectional view of a nonreflective portion of the single-plate typeaccording to the present embodiment;

[0087]FIG. 11 is a schematic diagram, based on an observation through atransmission electron microscope, illustrating a cross section of thenonreflective portion according to the present embodiment;

[0088]FIG. 12(a) is a cross-sectional view of a disk according to thepresent embodiment, and (b) is a crosssectional view of thenonreflective portion of the disk according to the present embodiment;

[0089]FIG. 13(a) is a diagram showing a physical arrangement ofaddresses on a legitimate CD according to the embodiment, and (b) is aphysical arrangement of addresses on an illegally duplicated CDaccording to the embodiment;

[0090]FIG. 14(a) is a diagram showing part (b) of FIG. 33 in furtherdetail, (b) is a diagram showing an equivalent data structure for ECCencoding/decoding, (c) is a diagram showing a mathematical equation forEDC computation, and (d) is a diagram showing a mathematical equationfor ECC computation:

[0091]FIG. 15 is a block diagram of a low-reflectivity position detectoraccording to the embodiment;

[0092]FIG. 16 is a diagram illustrating the principle of detectingaddress/clock positions of a low-reflectivity portion according to theembodiment;

[0093]FIG. 17 is a diagram showing a comparison of low-reflectivityportion address tables for a legitimate disk and a duplicated disk;

[0094]FIG. 18A is a flowchart illustrating a procedure for encryption,etc. using an RSA function according to the embodiment;

[0095]FIG. 18B is a flowchart illustrating a position information checkprocess according to the embodiment;

[0096]FIG. 19 is a flowchart illustrating a low-reflectivity positiondetecting program according to the embodiment;

[0097]FIG. 20 is a diagram showing a detected waveform of a first-layermarking signal according to the present embodiment;

[0098]FIG. 21 is a diagram showing a detected waveform of a second-layermarking signal according to the present embodiment;

[0099]FIG. 22 is a flowchart illustrating the function of a scrambleidentifier and the switching between drive ID and disk ID in a programinstallation process according to the present embodiment.

[0100]FIG. 23 is a block diagram of a stripe recording apparatusaccording to the embodiment;

[0101]FIG. 24 is a diagram showing a signal waveform and a trimmingpattern in RZ recording according to the embodiment;

[0102]FIG. 25 is a diagram showing a signal waveform and a trimmingpattern in NRZ recording;

[0103]FIG. 26 is a diagram showing a signal waveform and a trimmingpattern in PE-RZ recording according to the embodiment;

[0104]FIG. 27 is a diagram showing a top plan view of disk stripes,along with signal waveforms, according to the embodiment;

[0105]FIG. 28(a) is a perspective view of a converging unit according tothe embodiment, and (b) is a diagram showing a stripe arrangement and anemitting-pulse signal;

[0106]FIG. 29(a) is a perspective view of the converging unit, with abeam deflector appended thereto, according to the embodiment, and (b) isa diagram showing a stripe arrangement and an emitting-pulse signal;

[0107]FIG. 30 is a diagram showing the arrangement of stripes on a diskand the contents of control dada according to the embodiment;

[0108]FIG. 31 is a flowchart illustrating how control mode is switchedbetween CAV and CLV when playing back stripes according to theembodiment;

[0109]FIG. 32 is a diagram showing a stripe area and an address area ona disk according to the embodiment;

[0110]FIG. 33(a) is a diagram showing a data structure after ECCencoding according to the embodiment, (b) is a diagram showing a datastructure after ECC encoding according to the embodiment (when n=1), and(c) is a diagram showing an ECC error-correction capability according tothe embodiment;

[0111]FIG. 34 is a diagram showing the data structure of asynchronization code;

[0112]FIG. 35(a) is a diagram showing the configuration of an LPF, and(b) is a diagram showing a waveform filtered through the LPF;

[0113]FIG. 36(a) is a diagram showing a reproduced signal waveformaccording to the embodiment, and (b) is a diagram for explaining adimensional accuracy of a stripe according to the embodiment;

[0114]FIG. 37 is a diagram showing a synchronization code and a laseremitting pulse signal waveform;

[0115]FIG. 38 is a diagram showing a procedure for reading control datafor playback according to the embodiment;

[0116]FIG. 39 is a diagram showing a top plan view of a disk having apinhole-like optical marking as a physical feature according to theembodiment;

[0117]FIG. 40 is a diagram showing a procedure for playing back a PCAarea in a tracking ON condition according to the embodiment;

[0118]FIG. 41 is a block diagram of a playback apparatus implementingrotational speed control according to the embodiment;

[0119]FIG. 42 is a block diagram of a playback apparatus implementingrotational speed control according to the embodiment;

[0120]FIG. 43 is a block diagram of a playback apparatus implementingrotational speed control according to the embodiment;

[0121]FIG. 44 is a diagram illustrating a piracy prevention algorithmaccording to the embodiment;

[0122]FIG. 45 is a diagram for explaining barcode encryption accordingto the embodiment;

[0123]FIG. 46 is a diagram showing another application example of thebarcode according to the embodiment;

[0124]FIG. 47 is a perspective view showing a nonreflective portionformed in a two-layer disk according to the embodiment; and

[0125]FIG. 48 is a diagram showing a comparison of address coordinatepositions on different master disks according to the embodiment.

DESCRIPTION OF THE REFERENCE NUMERALS

[0126]584. LOW-REFLECTIVITY PORTION, 586. LOW REFLECTIVITY LIGHT AMOUNTDETECTOR, 587. LIGHT AMOUNT LEVEL COMPARATOR, 588. LIGHT AMOUNTREFERENCE VALUE, 599. LOW REFLECTIVITY PORTION START/END POSITIONDETECTOR, 600. LOW-REFLECTIVITY PORTION POSITION DETECTOR, 601.LOW-REFLECTIVITY PORTION ANGULAR POSITION SIGNAL OUTPUT SECTION, 602.LOW-REFLECTIVITY PORTION ANGULAR POSITION DETECTOR, 605.LOW-REFLECTIVITY PORTION START POINT, 606. LOW-REFLECTIVITY PORTION ENDPOINT, 607. TIME DELAY CORRECTOR, 816. DISK MANUFACTURING PROCESS, 817.SECONDARY RECORDING PROCESS, 818. DISK MANUFACTURING PROCESS STEPS, 819.SECONDARY RECORDING PROCESS STEPS, 820. SOFTWARE PRODUCTION PROCESSSTEPS, 830. ENCODING MEANS, 831. PUBLIC KEY ENCRYPTION, 833. FIRSTSECRET KEY, 834. SECOND SECRET KEY, 835. COMBINING SECTION, 836.RECORDING CIRCUIT, 837. ERROR-CORRECTION ENCODER, 838. REED-SOLOMONENCODER, 839. INTERLEAVER, 840. PULSE INTERVAL MODULATOR, 841. CLOCKSIGNAL GENERATOR, 908. ID GENERATOR, 909. INPUT SECTION, 910. RZMODULATOR, 913. CLOCK SIGNAL GENERATOR, 915. MOTOR, 915. ROTATIONSENSOR, 916. COLLIMATOR, 917. CYLINDRICAL LENS, 918. MASK, 919.CONVERGING LENS, 920. FIRST TIME SLOT, 921. SECOND TIME SLOT, 922. THIRDTIME SLOT, 923. STRIPE, 924. PULSE, 925. FIRST RECORDING REGION, 926.SECOND RECORDING REGION, 927. ECC ENCODER, 928. ECC DECODER, 929. LASERPOWER SUPPLY CIRCUIT, 930. STEPS (IN CAY PLAYBACK FLOWCHART), 931. BEAMDEFLECTOR, 932. SLIT, 933. STRIPE, 934. SUB-STRIPE, 935. DEFLECTIONSIGNAL GENERATOR, 936. CONTROL DATA AREA, 937. STRIPE PRESENCE/ABSENCEIDENTIFIER, 938. ADDITIONAL STRIPE PORTION, 939. ADDITIONAL STRIPEPRESENCE/ABSENCE IDENTIFIER, 940. STEPS (FOR STRIPE PRESENCE/ABSENCEIDENTIFIER PLAYBACK FLOWCHART), 941. OPTICAL MARKING (PINHOLE), 942.PE-RZ DEMODULATOR, 943. LPF, 944. ADDRESS AREA, 945. MAIN BEAM, 946.SUB-BEAM, 948. STRIPE REVERSE-SIDE RECORD IDENTIFIER, 949. STRIPE GAPPORTION, 950. SCANNING MEANS, 951. DATA ROW, 952. ECC ROW, 953.EDGE-SPACING DETECTING MEANS, 954. COMPARING MEANS, 955. MEMORY MEANS,956. OSCILLATOR, 957. CONTROLLER, 958. MOTOR DRIVE CIRCUIT, 959. BARCODEREADING MEANS, 963. MODE SWITCH, 964. HEAD MOVING MEANS, 965. FREQUENCYCOMPARATOR, 966. OSCILLATOR, 967. FREQUENCY COMPARATOR, 968. OSCILLATOR,969. MOTOR

DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0127] The preferred embodiments of the present invention will bedescribed below with reference to the accompanying drawings. In thedescription hereinafter given, position information for piracyprevention, which is a form of ID, is taken as an example of informationto be barcoded.

[0128] In the first-half part (I) of the description, a detailedexplanation will be given of the piracy prevention position informationas a form of ID, followed by a brief explanation of how the informationis converted into a barcode to complete an optical disk and how theoptical disk is played back. In the second-half part (II), the techniquefor barcoding the piracy prevention position information will bedescribed in further detail and in a concrete manner. More specifically,the first-half part (I) deals with (A) Manufacturing a disk, (B) Forminga marking by using laser light, (C) Reading the position information ofthe marking, (D) Encrypting the position information, converting theencrypted position information into a barcode, and writing the barcodein a pre-pit area of the optical disk in overwriting fashion, and (E)Playing back the optical disk on a player. The second-half part (II)first describes (A) Usefulness of the barcode for a laminated-typeoptical disk, then proceeds to (B) Barcoding the position information ofthe marking as a disk-unique ID, (C) Features of the barcode-recordedoptical disk format, methods of tracking control, and methods ofrotational speed control during reading of the barcode, and (D) Playingback the barcode-recorded optical disk. The second-half part (II)further deals in detail with (E) Manufacturing techniques forimplementing the-barcode recording method, followed by a briefexplanation of a barcode playback apparatus (player). Finally, adescription is given of (F) An example of the above barcode encryptionand another application example of the barcode. (I)

[0129] Before proceeding to the description of the above (A) to (E), wewill first describe a general process flow from disk manufacturing tothe completion of an optical disk by using the flowchart of FIG. 1.

[0130] In this patent specification, laser trimming is also referred toas laser marking, while a nonreflective optical marking portion issimply referred to as the barcode, stripe, marking, or optical markingor, sometimes, as the physical ID unique to a disk.

[0131] First, the software company performs software authoring insoftware production process 820. The completed software is deliveredfrom the software company to the disk manufacturing factory. In diskmanufacturing process 816 at the disk manufacturing factory, thecompleted software is input in step 818 a, a master disk is produced(step 818 b), disks are pressed (steps 818 e, 818 g), reflective filmsare formed on the respective disks (steps 818 f, 818 h), the two disksare laminated together (step 818 i), and a ROM disk such as a DVD or CDis completed (step 818 m, etc.).

[0132] The thus completed disk 800 is delivered to the software maker orto a factory under control of the software maker, where, in secondaryrecording process 817, an anti-piracy marking 584, such the one shown inFIG. 2, is formed (step 819 a), and accurate position information ofthis mark is read by a measuring means (step 819 b) to obtain theposition information which serves as the physical feature information ofthe disk. This physical feature information of the disk is encrypted instep 819 c. The encrypted information is converted to a PE-RZ-modulatedsignal which is then recorded in step 819 d as a barcode signal on thedisk by using a laser. The disk physical feature information may becombined together with software feature information for encryption instep 819 c.

[0133] The above processes will be described in further detail. That is,a disk fabrication process, a marking formation process, a markingposition reading process, and an encrypted information writing processfor an optical disk according to the present invention will be describedin detail with reference to FIGS. 4 and 5 and FIGS. 8 to 12. Asupplementary explanation will also be given dealing with a disk havingtwo reflective layers with reference to FIGS. 6 and 7. In the followingdescription, the marking formation process and the marking positionreading process are collectively called the secondary recording process.

[0134] (A) First, the disk fabrication process will be described. In thedisk fabrication process 806 shown in FIG. 4, first a transparentsubstrate 801 is pressed in step (1). In step (2), a metal such asaluminum or gold is sputtered to form a reflective layer 802. Anadhesive layer 804 formed from an ultraviolet curing resin is applied byspin coating to a substrate 803 formed in a different processing step,and the substrate 803 is bonded to the transparent substrate 801 havingthe reflective layer 802, and they are rotated at high speed to make thebonding spacing uniform. By exposure to external ultraviolet radiation,the resin hardens, thus firmly bonding the two substrates together. Instep (4), a printed layer 805 where a CD or DVD title is printed, isprinted by screen printing or offset printing. Thus, in step (4), theordinary laminated-type optical ROM disk is completed.

[0135] (B) Next, the marking formation process will be described withreference to FIGS. 4 and 5. In FIG. 4, a laser beam from a pulsed laser813 such as a YAG laser is focused through a converging lens 814 ontothe reflective layer 802, to form a nonreflective portion 815 as shownin step (6) in FIG. 5. That is, a distinct waveform, such as thewaveform (A) shown in step (7), is reproduced from the nonreflectiveportion 815 formed in step (6) in FIG. 5. By slicing this waveform, amarking detection signal such as shown by waveform (B) is obtained, fromwhich hierarchial marking position information comprising an address,such as shown in signal (d), and an address, a frame synchronizingsignal number, and a reproduced clock count, such as shown in signal(e), can be measured.

[0136] At the rising edge of the thus obtained marking detection signal,a specific address (indicated by address n in FIG. 5(d)) is read by theoptical pickup from within the plurality of addresses shown in FIG.5(d). FIG. 5(b) shows the physical location of the specific address inschematic form. On the other hand, FIG. 5(e) shows the logical structureof the data. As shown in FIG. 5(e), there are m frame synchronizationsignals under address n, and k reproduced clock pulses under each framesynchronization signal. Therefore, the position of the marking measuredby the optical pickup can be represented by address, framesynchronization signal number, and reproduced clock count.

[0137] As previously stated, a supplementary explanation will be givenbelow of an alternative type of disk (a two-layer laminated disk) withreference to FIGS. 6 and 7.

[0138]FIGS. 4 and 5 showed a disk generally known as a single-layerlaminated disk which has a reflective layer only on one substrate 801.On the other hand, FIGS. 6 and 7 show a disk generally known as atwo-layer laminated disk which has reflective layers on both substrates801 and 803. For laser trimming, the processing steps (5) and (6) arefundamentally the same for both types of disks, except with significantdifferences which are briefly described below. First, while thesingle-layer disk uses a reflective layer formed from an aluminum filmhaving reflectivity as high as 70% or over, in the two-layer disk thereflective layer 801 formed on the reading-side substrate 801 is asemi-transparent gold (Au) film having a reflectivity of 30%, while thereflective layer 802 formed on the print-side substrate 803 is the sameas that used in the single-layer disk. Second, as compared with thesingle-layer disk, the two-layer disk is required to have high opticalaccuracy; for example, the adhesive layer 804 must be opticallytransparent and be uniform in thickness, and the optical transparencymust not be lost due to laser trimming.

[0139] Parts (7), (8), and (9) of FIG. 7 show the signal waveformsobtained from the first layer of the two-recording-layer disk. Likewise,parts (10), (11), and (12) of FIG. 7 show the signal waveforms obtainedfrom the second layer of the two-recording-layer disk. The contents ofthese signal waveforms are essentially the same as those of thewaveforms described with reference to parts (a) to (c) of FIG. 5. Thewaveform from the second layer is similar to that from the first layer,though the signal level is lower than from the first layer. However,since the first and second layers are bonded together, relativepositional accuracy between them is random and can be controlled onlywith an accuracy of a few hundred microns. As will be described later,since the laser beam passes through the two reflective films, to make anillegal disk the position informations on the first and second layersfor the first mark, for example, have to be made to match the same valueon the legitimate disk. But making them match would require anear-submicron accuracy in laminating, and consequently, making illegaldisks of the two-layer type is practically impossible.

[0140] The technique for forming the nonreflective optical markingportion will be described in further detail in sections (a) to (d) belowwith reference to FIGS. 8 to 12, etc., dealing with the laminated typein comparison with a single-plate type. FIGS. 8(a) and (b) aremicrographs showing plan views of nonreflective optical markingportions, and FIG. 10(a) is a simplified schematic cross-sectional viewof a nonreflective portion of the two-layer laminated disk.

[0141] (a) Using a 5 μj/pulse YAG laser, a laser beam was applied to a500 angstrom aluminum layer lying 0.6 mm below the surface of a 1.2 mmthick ROM disk consisting of two 0.6 mm thick disks laminated together,and, as a result, a 12 μm wide slit-like nonreflective portion 815 wasformed, as shown in the X 750 micrograph of FIG. 8(a). In this X 750micrograph, no aluminum residues were observed on the nonreflectiveportion 815. Thick swollen aluminum layers, 2000 angstroms thick and 2μm wide, were observed along boundaries between the nonreflectiveportion 815 and reflective portions. As shown in FIG. 10(a), it wasconfirmed that no significant damage had occurred inside. In this case,the application of the pulsed laser presumably melted the aluminumreflective layer, causing a phenomenon of molten aluminum buildup alongthe boundaries on both sides due to the surface tension. We call this ahot melt surface tension (HMST) recording method. This is acharacteristic phenomenon observed only on a laminated disk 800. FIG. 11is a schematic diagram, based on an observation through a transmissionelectron microscope (TEM), illustrating a cross section of thenonreflective portion formed by the above laser trimming process. AndFIG. 11 shows that the adhesive layer of the disk has been removed byusing solvent.

[0142] In the figure, if the aluminum film swollen portion is 1.3 μmwide and 0.20 μm thick, the amount of increased aluminum in that portionis 1.3×(0.20−0.05)=0.195 μg m ². The amount of aluminum originallydeposited in a half portion (5 μm) of the laser exposed region (10 μm)was 5×0.05=0.250 μm². The difference is calculated as 0.250−0.195=0.055μm². In terms of length, this is equivalent to 0.055/0.05=1.1 μm. Thismeans that an aluminum layer of 0.05 μm thickness and 1.1 μm lengthremained, and therefore, it can be safely said that almost all aluminumwas drawn to the film swollen portion. Thus, the result of the analysisof the figure also verifies the explanation about the above-describedcharacteristic phenomenon.

[0143] (b) We will next deal with the case of a single-plate opticaldisk (an optical disk comprising a single disk). An experiment wasconducted by applying laser pulses of the same power to a 0.05 μm thickaluminum reflective film formed on a single-sided molded disk, of whichresult is shown in FIG. 8(b). As shown in the figure, aluminum residueswere observed, and since these aluminum residues cause reproductionnoise, it can be seen that the single-plate type is not suitable forsecondary recording of optical disk information of which a high densityand a low error rate are demanded. Furthermore, unlike the laminateddisk, in the case of the single-plate disk, the protective layer 862 isinevitably damaged. as shown in FIG. 10(b), when the nonreflectiveportion is subjected to laser trimming. The degree of damage depends onthe laser power, but the damage cannot be avoided even if the laserpower is controlled accurately. Moreover, according to our experiment,the printed layer 805 formed by screen printing to a thickness of a fewhundred microns on the protective layer 862 was damaged when its thermalabsorptance was high. In the case of the single-plate disk, to addressthe problem of protective layer damage, either the protective layer hasto be applied once again or the laser cut operation should be performedbefore depositing the protective layer. In any case, the single-platetype may present a problem in that the laser cut process has to beincorporated in the pressing process. This limits the application of thesingle-plate disk despite its usefulness.

[0144] (c) A comparison between single-plate disk and laminated disk hasbeen described above, using a two-layer laminated disk as an example. Asis apparent from the above description, the same effect as obtained withthe two-layer laminated disk can be obtained with the single-layerlaminated disk. Using FIGS. 12(a), 12(b), etc., a further descriptionwill be given dealing with the single-layer laminated disk type. Asshown in FIG. 12(a), the reflective layer 802 has the transparentsubstrate 801 of polycarbonate on one side, and the hardened adhesivelayer 804 and a substrate on the other side, the reflective layer 802thus being hermetically sealed therebetween. In this condition, pulsedlaser light is focused thereon for heating; in the case of ourexperiment, heat of 5 μJ/pulse is applied to a circular spot of 10 to 20μm diameter on the reflective layer 802 for a short period of 70 ns. Asa result, the temperature instantly rises to 600° C., the melting point,melting state is caused. By heat transfer, a small portion of thetransparent substrate 801 near the spot is melted, and also a portion ofthe adhesive layer 804 is melted. The molted aluminum in this state iscaused by surface tension to build up along boundaries 821 a and 821 b,with tension being applied to both sides, thus forming buildups 822 aand 822 b of hardened aluminum, as shown in FIG. 12(b). Thenonreflective portion 584 free from aluminum residues is thus formed.This shows that a clearly defined nonreflective portion 584 can beobtained by laser-trimming the laminated disk as shown in FIGS. 10(a)and 12(a). Exposure of the reflective layer to the outside environmentdue to a damaged protective layer, which was the case with thesingle-plate type, was not observed even when the laser power wasincreased more than 10 times the optimum value. After the lasertrimming, the nonreflective layer 584 has the structure shown in FIG.12(b) where it is sandwiched between the two transparent substrates 801,803 and sealed with the adhesive layer 804 against the outsideenvironment, thus producing the effect of protecting the structure fromenvironmental effects.

[0145] (d) Another benefit of laminating two disks together will bedescribed next. Then secondary recording is made in the form of abarcode, an illegal manufacturer can expose the aluminum layer byremoving the protective layer in the case of a single-plate disk, asshown in FIG. 10(b). This gives rise to a possibility that nonecrypteddata may be tampered with by redepositing an aluminum layer over thebarcode portion on a legitimate disk and then laser-trimming a differentbarcode. For example, if the ID number is recorded in plaintext orseparately from main ciphertext, in the case of a single-plate disk itis possible to alter the ID number, enabling illegal use of the softwareby using a different password. However, if the secondary recording ismade on the laminated disk as shown in FIG. 10(a), it is difficult toseparate the laminated disk into two sides. In addition, when removingone side from the other, the aluminum reflective film is partiallydestroyed. When the anti-piracy marking is destroyed, the disk will bejudged as being a pirated disk and will not run. Accordingly, whenmaking illegal alterations to the laminated disk, the yield is low andthus illegal alterations are suppressed for economic reasons.Particularly, in the case of the two-layer laminated disk, since thepolycarbonate material has temperature/humidity expansion coefficients,it is nearly impossible to laminate the two disks, once separated, byaligning the anti-piracy markings on the first and second layers with anaccuracy of a few microns, and to mass produce disks. Thus, thetwo-layer type provides a greater effectiveness in piracy prevention. Itwas thus found that a clearly defined slit of a nonreflective portion584 can be obtained by laser-trimming the laminated disk 800.

[0146] The technique for forming the nonreflective optical markingportion has been described in (a) to (d) above.

[0147] (C) Next, the process of reading the position of the thus formedmarking will be described.

[0148]FIG. 15 is a block diagram showing a low reflectivity light amountdetector 586 for detecting the nonreflective optical marking portion.along with its adjacent circuitry, in an optical disk manufacturingprocess. FIG. 16 is a diagram illustrating the principle of detectingaddress/clock positions of the low reflectivity portion. For convenienceof explanation, the following description deals with the operatingprinciple when a read operation is performed on a nonreflective portionformed on an optical disk constructed from a single disk. It will berecognized that the same operating principle also applies to an opticaldisk constructed from two disks laminated together.

[0149] As shown in FIG. 15, the disk 800 is loaded into a markingreading apparatus equipped with a low reflectivity position detector 600to read the marking, and in this case, since a signal waveform 823 dueto the presence and absence of pits and a signal waveform 824 due to thepresence of the nonreflective portion 584 are significantly different insignal level, as shown in the waveform diagram of FIG. 9(a), they can beclearly distinguished using a simple circuit.

[0150]FIG. 9(a) is a diagram showing the waveform of a playback signalfrom a PCA area, described later, containing the nonreflective portion584 formed by laser light. FIG. 9(b) is a diagram showing the waveformof FIG. 9(a) but with a different time axis.

[0151] By removing the reflective film by laser light, as describedabove, a waveform easily distinguishable from that of a pit signal isobtained. Rather than forming an anti-piracy identification mark byremoving the reflective film by laser light, as described above, theanti-piracy mark may be formed by changing the shape of pits on themaster disk. This method will be described below. FIG. 9(c) shows thewaveform of a playback signal when the anti-piracy identification markwas formed by making pits longer than other data pits on the masterdisk. It can be seen from the diagram that the waveform 824 p of theanti-piracy identification mark is distinguishable from the waveform ofother pit data. In this way, a waveform similar to that obtained fromthe PCA area described later can be obtained by forming longer pits onthe master disk; in this case, however, the waveform is a littledifficult to distinguish as compared to the waveforms shown in parts (a)and (b) of FIG. 9.

[0152] By removing the reflective film by laser light, as describedabove, a waveform easily distinguishable from that of a pit signal isobtained. Rather than forming the barcode of the invention by removingthe reflective film by laser light, as described above, the barcode maybe formed by changing the shape of pits on the master disk. This masterdisk method will be described below. FIG. 9(d) is a plan view showing aportion of a master disk wherein pits 824 q in a few hundred tracks onthe master disk are made longer than other data pits and made equal tothe barcode bar width t (=10 μm). Since reflectivity drops in thislonger-bit area, a waveform 824 p as shown in FIG. 9(c) is obtained. Itcan be seen from the diagram that the waveform 824 p by the master diskmethod is distinguishable from the waveform of other pit data. In thisway, a waveform similar to that obtained from the PCA area describedlater can be obtained by the master disk method; in this case, however,the waveform is a little difficult to distinguish as compared to thewaveforms shown in parts (a) and (b) of FIG. 9.

[0153] As shown in FIG. 16(1), the start and end positions of thenonreflective portion 564 having the above waveform can be easilydetected by the low reflectivity light amount detector 586 shown in theblock diagram of FIG. 15. Using the reproduced clock signal as thereference signal, position information is obtained in a low reflectivityposition information output section 596. FIG. 16(1) shows across-sectional view of the optical disk.

[0154] As shown in FIG. 15, a comparator 587 in the low reflectivitylight amount detector 586 detects the low reflectivity light portion bydetecting an analog light reproduced signal having a lower signal levelthan a light amount reference value 588. During the detection period, alow reflectivity portion detection signal of the waveform shown in FIG.16(5) is output. The addresses and clock positions of the start positionand end position of this signal are measured.

[0155] The reproduced light signal is waveshaped by a waveform shapingcircuit 590 having an AGC 590 a, for conversion into a digital signal. Aclock regenerator 38 a regenerates a clock signal from the waveshapedsignal. An EFM demodulator 592 in a demodulating section 591 demodulatesthe signal, and an ECC corrects errors and outputs a digital signal. TheEFM-demodulated signal is also fed to a physical address output section593 where an address of MSF, from Q bits of a subcode in the case of aCD, is output from an address output section 594 and a synchronizingsignal, such as a frame synchronizing signal, is output from asynchronizing signal output section 595. From the clock regenerator 38a, a demodulated clock is output.

[0156] In a low reflectivity portion address/clock signal positionsignal output section 596, a low reflectivity portion start/end positiondetector 599 accurately measures the start position and end position ofthe low reflectivity portion 584 by using an (n−1) address outputsection 597 and an address signal as well as a clock counter 598 and asynchronizing clock signal or the demodulated clock. This method will bedescribed in detail by using the waveform diagrams shown in FIG. 16. Asshown in the cross-sectional view of the optical disk in FIG. 16(1), thelow reflectivity portion 584 of mark number 1 is formed partially. Areflection selope signal such as shown in FIG. 16(3), is output, thesignal level from the reflective portion being lower than the lightamount reference value 588. This is detected by the light levelcomparator 587, and a low reflectivity light detection signal, such asshown in FIG. 16(5), is output from the low reflectivity light amountdetector 586. As shown by a reproduced digital signal in FIG. 16(4), nodigital signal is output from the mark region since it does not have areflective layer.

[0157] Next, to obtain the start and end positions of the lowreflectivity light detection signal, the demodulated clock orsynchronizing clock shown in FIG. 16(6) is used along with addressinformation. First, a reference clock 605 at address n in FIG. 16(7) ismeasured, When the address immediately preceding the address n isdetected by the (n−1) address output section 597, it is found that thenext sync 604 is a sync at address n. The number of clocks from thesynch 604 to the reference clock 605, which is the start position of thelow reflectivity light detection signal, is counted by the clock counter598. This clock count is defined as a reference delay time TD which ismeasured by a reference delay time TD measuring section 608 for storagetherein.

[0158] The circuit delay time varies with reproduction apparatus usedfor reading, which means that the reference delay time TD variesdepending on the reproduction apparatus used. Therefore, using the TD, atime delay corrector 607 applies time correction, and the resultingeffect is that the start clock count for the low reflectivity portioncan be measured accurately if reproduction apparatus of differentdesigns are used for reading. Next, by finding the clock count. and thestart and end addresses for the optical mark No. 1 in the next track,clock m+14 at address n+12 is obtained, as shown in FIG. 16(8). SinceTD=m+2, the clock count is corrected to 12, but for convenience ofexplanation, n+14 is used. We will describe another-method, whicheliminates the effects of varying delay times without having to obtainthe reference delay time TD in the reproduction apparatus used forreading. This method can check whether the disk is a legitimate disk ornot by checking whether the positional relationship of mark 1 at addressn in FIG. 16(8) relative to another mark 2 matches or not. That is, TDis ignored as a variable, and the difference between the position,A1=a1+TD, of mark 1 measured and the position, A2=a2+TD, of mark 2measured is obtained, which is given as A1−A2=al−a2. At the same time,it is checked whether this difference matches the difference, a1−a2,between the position al of the decrypted mark 1 and the positioninformation a2 of the mark 2, thereby judging whether the disk is alegitimate disk or not. The effect of this method is that the positionscan be checked after compensating for variations of the reference delaytime TD by using a simpler constitution.

[0159] (D) Next, the encrypted information writing process will bedescribed. The position information read in the process (C) is firstconverted into ciphertext or “signed” with a digital signature. Then,the marking position information thus encrypted or signed is convertedinto a barcode as an ID unique to the optical disk, and the barcode isrecorded in overwriting fashion in a prescribed region of a pre-pit areaon the optical disk. Barcode patterns 584 c-584 e in FIG. 2(a) indicatethe barcode written to the prescribed region of the pre-pit area, thatis, in the innermost portion of the pre-pit area.

[0160] Parts (1) to (5) of FIG. 3 show the process from the recording ofthe barcode to the demodulation of the barcode detection signal by aPE-RZ modulated signal demodulator. In part (1) of FIG. 3, thereflective layer is trimmed by a pulsed laser, and a barcode-liketrimming pattern, such as shown in part (2) of the figure, is formed. Atthe playback apparatus (player), an envelope waveform some portions ofwhich are missing, as shown in part (3) of the figure, is obtained. Themissing portions result in the generation of a low level signal thatcannot occur with a signal generated from an ordinary pit. Therefore,this signal is sliced by a second slice level comparator to obtain alow-reflectivity portion detection signal as shown in part (4) of thefigure. In part (5) of the figure, the playback signal of the barcode isdemodulated from this low-reflectivity portion detection signal by thePE-RZ modulated signal demodulator 621 which will be described in detailin the second-half part (II). It will be appreciated that, instead ofthe P-ERZ modulated signal demodulator 621, a pulse-width modulatedsignal demodulator (PWM demodulator) may be used, in which case also, asimilar effect can be obtained.

[0161] When applying the above encryption or digital signature, a secretkey of a public key encryption function is used. As an example of theencryption, FIGS. 18A and 18B show an encryption process using an RSAfunction.

[0162] As shown in FIG. 18A, the process consists of the following majorroutines: step 735 a where marking position information is measured atthe optical disk maker, step 695 where the position information isencrypted (or a digital signature is appended), step 698 where theposition information is decrypted (or the signature is verified orauthenticated) in the reproduction apparatus, and step 735 w where acheck is made to determine whether the disk is a legitimate optical diskor not.

[0163] First, in step 735 a, the marking position information on theoptical disk is measured in step 735 b. The position information is thencompressed in step 735 d, and the compressed position information H isobtained in step 735 e.

[0164] In step 695, the ciphertext of the compressed positioninformation H is constructed. First, in step 695, a secret key, d, of512 or 1024 bits, and secret keys, p and q, of 256 or 512 bits, are set,and in step 695 b, encryption is performed using an RSA function. Whenthe position information H is denoted by M, M is raised to d-th powerand mod n is calculated to yield ciphertext C. In step 695 d, theciphertext C is recorded on the optical disk. The optical disk is thuscompleted and is shipped (step 735 k).

[0165] In the reproduction apparatus, the optical disk is loaded in step735 m, and the ciphertext C is decrypted in step 698. More specifically,the ciphertext C is recovered in step 698 e, and public keys, e and n,are set in step 698 f; then in step b, to decrypt the ciphertext C, theciphertext C is raised to e-th power and the mod n of the result iscalculated to obtain plaintext M. The plaintext M is the compressedposition information H. An error check may be performed in step 698 g.If no errors, it is decided that no alterations have been made to theposition information, and the process proceeds to the disk check routine735 w shown in FIG. 18B. If an error is detected, it is decided that thedata is not legitimate one, and the operation is stopped.

[0166] In the next step 736 a, the compressed position information H isexpanded to recover the original position information. In step 736 c,measurements are made to check whether the marking is actually locatedin the position on the optical disk indicated by the positioninformation. In step 736 d, it is checked whether the difference betweenthe decrypted position information and the actually measured positioninformation falls within a tolerance. If the check is OK in step 736 e,the process proceeds to step 736 h to output software or data or executeprograms stored on the optical disk. If the check result is outside thetolerance, that is, if the two pieces of position information do notagree, a display is produced to the effect that the optical disk is anillegally duplicated one, and the operation is stopped in step 736 g.RSA has the effect of reducing required capacity since only theciphertext need be recorded.

[0167] (E) The processing steps in the optical disk manufacturingprocess have been described above. Next, the constitution and operationof a reproduction apparatus (player) for reproducing the thus completedoptical disk on a player will be described with reference to FIG. 44.

[0168] In the figure, the construction of an optical disk 9102 will bedescribed first. A marking 9103 is formed on a reflective layer (notshown) deposited on the optical disk 9102. In the manufacturing processof the optical disk, the position of the marking 9103 was detected byposition detecting means, and the detected position was encrypted asmarking position information and written on the optical disk in the formof a barcode 9104.

[0169] Position information reading means 9101 reads the barcode 9104,and decrypting means 9105 contained therein decrypts the contents of thebarcode for output. Marking reading means 9106 reads the actual positionof the marking 9103 and outputs the result. Comparing/judging means 9107compares the decrypted result from the decrypting means 9105 containedin the position information reading means 9101 with the result ofreading by the marking reading means 9106, and judges whether the twoagree within a predetermined allowable range. If they agree, areproduction signal 9108 for reproducing the optical disk is output; ifthey do not agree, a reproduction stop signal 9109 is output. Controlmeans (not shown) controls the reproduction operation of the opticaldisk in accordance with these signals; when the reproduction stop signalis output, an indication to the effect that the optical disk is anillegal duplicated disk is displayed on a display (not shown) and thereproduction operation is stopped. In the above operation, it will berecognized that it is also possible for the marking reading means 9106to use the decrypted result from the decrypting means 9105 when readingthe actual position of the marking 9103.

[0170] Namely in this case, the marking reading means 9106 checkswhether the marking is actually located in the position on the opticaldisk indicated by the position information which is decrypted by thedecrypting means 9105.

[0171] Thus the reproduction apparatus of the above construction candetect an illegally duplicated optical disk and stop the reproductionoperation of the disk, and can prevent illegal duplicates practically.(II)

[0172] We finish here the description of the first-half part (I), andnow proceed to the description of the second-half part (II). This partfocuses particularly on techniques, including a barcode formationmethod, used when barcoding the above marking position information (IDinformation) as a disk-unique ID.

[0173] (A) Features of the optical disk of the present invention will bedescribed.

[0174] When a barcode is recorded by laser trimming on theabove-described single-plate disk, the protective layer 862 isdestroyed, as explained in connection with FIG. 10(b). Therefore, afterlaser trimming at a press factory, the destroyed protective layer 862has to be reformed at the press factory.

[0175] This means that a barcode cannot be recorded on the optical diskat a software company or a dealer that does not have the necessaryequipment. The problem expected here is that the application of barcoderecording is greatly limited.

[0176] On the other hand, when the marking position information wasrecorded as a barcode by laser trimming on the laminated-type disk ofthe invention formed from two transparent substrates laminated together,it was confirmed that the protective layer 804 remained almostunchanged, as already explained in connection with FIG. 10(a). This wasconfirmed by experiment by observing the disk under an opticalmicroscope of 800× magnification. It was also confirmed that no changehad occurred to the reflective film in the trimmed portion after anenvironmental test of 96 hours at a temperature of 85° C. and a humidityof 95%.

[0177] In this way, when the laser trimming of the present invention isapplied to a laminated disk such as a DVD, there is no need to reformthe protective layer at the factory. This offers a great advantage inthat a barcode can be recorded by trimming on the optical disk at aplace other than the press factory, for example, at a software companyor a dealer. The usefulness of barcode recording on the laminated-typeoptical disk was thus confirmed.

[0178] In this case, since the secret key information for encryptionthat the software company keeps need not be delivered to a party outsidethe company, security increases greatly, particularly when securityinformation such as a serial number for copy prevention is recorded as abarcode in addition to the above-described position information.Furthermore, in the case of a DVD, since the barcode signal can beseparated from DVD pit signals by setting the trimming line width at avalue greater than 14 T or 1.82 microns, as will be described later, thebarcode signal can be recorded in the pit recording area on the DVD insuperimposing fashion. The barcode formed in this way offers the effectthat the barcode can be read by the optical pickup used to read the pitsignal. This effect can be obtained not only with the laminated-typedisk but also with the previously described single-plate disk.

[0179] Thus, by applying the barcode forming method and modulationrecording method of the invention to a laminated-type disk such as aDVD, a laminated-type optical disk can be provided that permitssecondary recording after shipment from the factory. The abovedescription has dealt mainly with a case in which the barcode is formedby laser trimming on a laminated-type disk of a two-layer, single-sidedstructure (with two reflective layers formed on one side). Thissingle-sided, two-layered optical disk is the type of disk that permitsplayback of both sides from one side of the disk without having to turnover the disk.

[0180] On the other hand, when trimming is performed on a double-sided,laminated-type optical disk that needs turning over when playing backthe reverse side, the laser light passes through the two reflectivefilms each formed on one side of the disk. Therefore, the barcode can beformed simultaneously on both sides. This provides an advantage formedia fabrication in that the barcode can be recorded simultaneously onboth sides in a single step.

[0181] In this case, when the optical disk is turned over to play backthe reverse side on a playback apparatus, the barcode signal is playedback in just the opposite direction to the direction that the barcodesignal on the front side is played back. A method for identifying thereverse side is therefore needed. This will be described in detaillater.

[0182] (B) Referring now to FIGS. 23 to 26, etc., we will describe theconstruction and operation of an optical disk barcode forming apparatusfor converting the marking position information (ID number) into abarcode as a disk-unique ID and for recording the barcode in aprescribed region of a pre-pit area. A barcode recording method, etc.will also be described.

[0183] (a) First, the optical disk barcode recording apparatus will bedescribed with reference to FIG. 23.

[0184]FIG. 23 is a diagram showing the configuration of the barcoderecording apparatus for implementing an optical disk barcode formingmethod in one embodiment of the present invention. In the abovementioned embodiment, data to be barcoded is the data of encryptedversion of marking position information. But the data to be barcode isnot restricted to the above embodiment. It may include, for example,input data and an ID number issued from an ID generator 908, as shown inFIG. 23, or any other kind of data.

[0185] In FIG. 23, the input data and the ID number issued from the IDgenerator 908 are combined together in an input section 909; in anencryption encoder 830, the combined data is subjected to signature orencryption using an RSA function, etc. as necessary, and in an ECCencoder 907, error-correction coding and interleaving are applied. Theencryption process and the playback process will be described in detaillater by way of example with reference to FIG. 45.

[0186] The data is then fed into an RZ modulator 910 wherephase-encoding (PE) RZ modulation to be described later is performed.The modulating clock used here is created by a clock signal generator913 in synchronism with a rotation pulse from a motor 915 or a rotationsensor 915 a.

[0187] Based on the RZ-modulated signal, a trigger pulse is created in alaser emitting circuit 911, and is applied to a laser 912 such as a YAGlaser established by a laser power supply circuit 929. The laser 912thus driven emits pulsed laser light which is focused through aconverging unit 914 onto the reflective film 802 on the laminated disk800, removing the reflective film in a barcode pattern. Theerror-correction method will be described in detail later. Forencryption, a public key cipher, such as the one shown in FIG. 18, isappended as a signature to the serial number with a secret key that thesoftware company has. In this case, since no one other than the softwarecompany has the secret key and therefore cannot append a legitimatesignature to a new serial number, this has an enormous effect inpreventing illegal manufacturers from issuing a serial number. Since thepublic key cannot be deciphered, as previously described, the securityis greatly enhanced. Disk piracy can thus be prevented even when thepublic key is recorded on the disk for delivery.

[0188] The converging unit 914 in the optical disk barcode formingapparatus of the present embodiment will be described below in moredetail.

[0189] As shown in FIG. 28(a), light emitted from the laser 912 entersthe converging unit 914 where the entering light is converted by acollimator 916 into a parallel beam of light which is then converged inonly one plane by a cylindrical lens 917, thus producing a stripe oflight. This light is limited by a mask 918, and is focused through aconverging lens 919 onto the reflective film 802 on the optical disk toremove the film in a stripe pattern. A stripe such as shown in FIG.28(b) is thus formed. In PE modulation, stripes are spaced apart atthree different intervals, 1T, 2T, and 3T. If this spacing is displaced,jitter occurs and the error rate rises. In the present invention, theclock generator 913 generates a modulating clock in synchronism with arotation pulse from the motor 915, and supplies this modulating clock tothe modulator 910 to ensure that each stripe 923 is recorded at acorrect position in accordance with the rotation of the motor 915, thatis, with the rotation of the disk 800. This has the effect of reducingjitter. Alternatively, a laser scanning means 950, such as shown in FIG.3(1), may be provided by which a continuous-wave laser is scanned in aradial direction to form a barcode.

[0190] (b) Next, a barcode recording method, etc., for forming a barcodeusing the above-described barcode recording apparatus, will be describedwith reference to FIG. 24 to 26.

[0191]FIG. 24 shows signals coded with RZ recording (polarityreturn-to-zero recording) of the invention and trimming patterns formedcorresponding to them. FIG. 25 shows signals coded with a conventionalbarcode format and trimming patterns formed corresponding to them.

[0192] The present invention uses RZ recording, as shown in FIG. 24. Inthis RZ recording, one unit time is divided into a plurality of timeslots, for example, a first time slot 920 a, a second time slot 921, athird time slot 922, and so on. When data is “00”, for example, a signal924 a of a duration shorter than the period of the time slot, that is,the period T of a channel clock, is recorded in the first time slot 920a, as shown in part (1) in FIG. 26. The pulse 924 a whose duration isshorter than the period T of the recording clock is output between t=T1and t=T2. In this case, using a rotation pulse from the rotation sensor915 a on the motor 915, the clock signal generator 913 generates amodulation clock pulse as shown in part (1) of FIG. 24; by performingthe recording in synchronism with the clock pulse, the effects ofrotational variation of the motor can be eliminated. In this way, asshown in part (2) of FIG. 24, a stripe 923 a indicating “00” is recordedon the disk within a recording region 925 a, the first of the fourrecording regions shown, and a circular barcode such as shown in part(1) of FIG. 27 is formed.

[0193] Next, when data is “01”, a pulse 924 b is recorded in the secondtime slot 921 b between t=T2 and t=T3, as shown in part (3) in FIG. 24.In this way, a stripe 923 b is recorded on the disk within a recordingregion 926 b, the second region from the left, as shown in part (4) ofFIG. 24.

[0194] Next, when recording data “10” and “11”, these data are recordedin the third time slot 922 a and fourth time slot, respectively.

[0195] Here, for comparison purposes, NRZ recording (non-return-to-zerorecording) used for conventional barcode recording will be describedwith reference to FIG. 25.

[0196] In NZR recording, pulses 928 a and 928 b, each having a widthequal to the period T of time slot 920 a, are output, as shown in part(1) of FIG. 25. In RZ recording, the width of each pulse is 1/nT; on theother hand, in the case of NZR recording, a pulse as wide as T isneeded, and furthermore, when T appears successively, a pulse of doubleor triple width, 2T or 3T, becomes necessary, as shown in part (3) ofFIG. 25. In the case of laser trimming such as described in the presentinvention, changing the laser trimming width is practically difficultsince it necessitates changing settings, and therefore, NRZ is notsuitable. As shown in part (2) of FIG. 25, stripes 929 a and 929 b arerespectively formed in the first and third recording regions 925 a and927 a from the left, and in the case of data “10”, a stripe 929 b ofwidth 2T is recorded in the secondhand third recording regions 929 b and927 b from the left, as shown in part (4) of FIG. 25.

[0197] In the conventional NRZ recording, the pulse widths are 1T and2T, as shown in parts (1) and (3) of FIG. 25; it is therefore apparentthat NRZ recording is not suitable for the laser trimming of the presentinvention. According to the laser trimming of the present invention, abarcode is formed as shown in the experiment result shown in FIG. 8(a),but since trimming line width differs from disk to disk, it is difficultto precisely control the line width; when trimming the reflective filmon a disk, the trimming line width varies depending on variations inlaser output, thickness and material of the reflective film, and thermalconductivity and thickness of the substrate. Further, forming slots ofdifferent line widths on the same disk will result in an increasedcomplexity of the recording apparatus. For example, in the case of theNZR recording used for product barcode recording, as shown in parts (1)and (2) of FIG. 25, the trimming line width must be made to preciselycoincide with the period 1T of the clock signal, or 2Tor 3T, that is,with nT. It is particularly difficult to record various line widths suchas 2T and 3T by varying the line width for each bar (each stripe). Sincethe conventional product barcode format is an NRZ format, if this formatis applied to the laser-recorded barcode of the present invention, thefabrication yield will decrease because it is difficult to preciselyrecord varying line widths such as 2T and 2T on the same disk;furthermore, stable recording cannot be done since the laser trimmingwidth varies. This makes demodulation difficult. Using RZ recording, thepresent invention has the effect of achieving stable digital recordingeven if the laser trimming width varies. Furthers the invention offersthe effect of simplifying the construction of the recording apparatussince RZ recording requires only one kind of line width and the laserpower therefore need not be modulated.

[0198] As described, by employing the above RZ recording for opticaldisk barcode recording according to the invention, there is offered theeffect of ensuring stable digital recording.

[0199] An example of the phase-encoding (PE) modulation of RZ recordingwill be described with reference to FIG. 26.

[0200]FIG. 26 shows signals and an arrangement of stripes when the RZrecording shown in FIG. 24 is PE-modulated. As shown, data “0” isrecorded in the left-hand time slot 920 a of the two time slots 920 aand 921 a; on the other hand, data “1” is recorded in the right-handtime slot 921 a, as shown in part (3) of FIG. 26. On the disk, data “0”is recorded as a stripe 923 a in the left-hand recording region 925 aand data “1” as a stripe 923 b in the right-hand recording region 926 b,as shown in parts (2) and (4) of FIG. 26, respectively. Thus, for data“010”, a pulse 924 c is output in the left-hand time slot for “0”, apulse 924 d is output in the right-hand time slot for “1”, and a pulse924 e is output in the left-hand time slot for “0”, as shown in part (5)of FIG. 26; on the disk, the first stripe is formed in the left-handposition, the second stripe in the right-hand position, and the thirdstripe in the left-hand position, by laser trimming. FIG. 26(5) showssignals modulated with data “010”. As can be seen, a signal is alwaysavailable for every channel bit. That is, since the signal density isconstant, the DC component does not vary. Since the DC component doesnot vary, PE modulation is resistant to variation in low-frequencycomponents even if a pulse edge is detected during playback. This hasthe effect of simplifying playback demodulator circuitry of the diskplayback apparatus. Furthermore, since one signal 923 is alwaysavailable for every channel clock 2T, this has the effect of being ableto reproduce a synchronization clock for a channel clock without using aPLL.

[0201] A circular barcode, such as shown in FIG. 27(1), is thus formedon the disk. When data “01000”, shown in part FIG. 27(4), is recorded,in the PE-RZ modulation of the invention a barcode 923 a having the samepattern as the recorded signal shown in part (3) is recorded as shown inpart (2). When this barcode is played back by an optical pickup, asignal waveform, such as shown in part (5) REPRODUCED SIGNAL, is outputwith portions thereof dropped corresponding to missing portions of apit-modulated signal where no reflection signals are obtained due toremoval of the reflective film, as explained with reference to part FIG.5(6). By passing this reproduced signal through the second-order orthird-order LPF filter 934 shown in FIG. 35(a), the filtered signalwaveform shown in FIG. 27(6) is obtained. By slicing this signal by alevel slicer, reproduced data “01000” of part (7) is demodulated.

[0202] (C) We will next describe features of the optical disk formatwith a barcode formed in the above manner, tracking control methods, androtational speed control methods that can be used when playing back theoptical disk.

[0203] (a) We will first describe the features of the optical diskformat with a barcode formed according to the present embodiment, whiledealing with an example of a condition that permits tracking controlduring playback (this condition is also referred to as the tracking ONcondition). A playback operation using tracking control is shown in FIG.40, and its details will be given later.

[0204] In the case of a DVD disk in the present embodiment, all data arerecorded in pits with CLV, as shown in FIG. 30. Stripes 923 (forming abarcode) are recorded with CAV. CLV recording means recording withconstant linear velocity, while CAV recording means recording withconstant angular velocity.

[0205] In the present invention, the stripes 923 are recorded with CAV,superimposed on a pre-pit signal in a lead-in data area holding anaddress which is recorded with CLV. That is, the data is overwrittenwith the stripes. In the present invention, the pre-pit signal area mapsinto all the data areas where pits are formed. The prescribed region ofthe pre-pit signal area, as mentioned in the present invention,corresponds to an inner portion of the optical disk; this region is alsocalled a post-cutting area (PCA). In this PCA area, the barcode isrecorded with CAV, superimposed on pre-bit signals. In this way, the CLVdata is recorded with a pit pattern from the master disk, while the CAVdata is recorded with laser-removed portions of the reflective film.Since the barcode data is written in overwriting fashion, pits arerecorded between the barcode stripes 1T, 2T, and 3T. Using this pitinformation, optical head tracking is accomplished, and Tmax or Tmin ofthe pit information can be detected; therefore, motor rotational speedis controlled by detecting this signal. To detect Tmin, the relationbetween the trimming width t of stripe 923 a and the pit clock T (pit)should be t>14T (pit), as shown in FIG. 30, to achieve the above effect.If t is shorter than 14T, the pulse width of the signal from the stripe923 a becomes equal to the pulse width of the pit signal, anddiscrimination between them is not possible, so that the signal from thestripe 923 a cannot be demodulated. To enable pit address information tobe read at the same radius position as the stripes, an address area 944is provided longer than a unit of one address of pit information, asshown in FIG. 32; address information can thus be obtained, making itpossible to jump to the desired track. Furthermore, the ratio of thestripe area to the non-stripe area, that is, the duty ratio, is madeless than 50%, i.e., T(S)<T(NS); since the effective reflectivitydecreases only by 6 dB, this has the effect of ensuring stable focusingof the optical head.

[0206] Next, we will describe an example of a condition in whichtracking control cannot be applied during playback (this condition isalso referred to as the tracking OFF condition).

[0207] Since the stripes 923 are written over pits, interrupting pitsignals and preventing correct playback of the pit data, trackingcontrol may not be possible on some players. In such players, the strips923, which are CAV data, can be read by the optical pickup by applyingrotational control using a rotational pulse from a Hall element, etc. inthe motor 17.

[0208]FIG. 31 shows a flowchart illustrating a procedure for operationsin a playback apparatus when pit data in the optical tracks in thestripe area cannot be correctly played back.

[0209] In FIG. 31, when a disk is inserted in step 930 a, the opticalhead is moved by a prescribed distance to the inner portion in step 930b. The optical head is thus positioned on the area where the stripes 923of FIG. 30 are recorded.

[0210] Here, it is not possible to correctly playback data from all thepits recorded in the stripe area 923. In this case, therefore, usualrotation phase control cannot be applied for the playback of the pitdata recorded with CLV.

[0211] In step 930 c, rotational speed control is applied by using arotational sensor of a Hall element in the motor or by measuring theT(max) or T(min) or frequency of a pit signal. If it is determined instep 930 i that there are no stripes, the process jumps to step 930 f.If there are stripes, the barcode is played back in step 930 d, and whenplayback of the barcode is completed in step 930 e, the optical head ismoved in step 930 f to an outer area where no stripes are recorded. Inthis area, since no stripes are recorded, the pits are played backcorrectly and accurate focus and tracking servo are achieved. Since thepit signal can be played back, usual rotation phase control can beperformed to rotate the disk with CLV. As a result, in step 930 h, thepit signal is played back correctly.

[0212] By switching between the two rotation control modes, i.e., therotational speed control and the rotation phase control by pit signals,the effect is obtained that two different kinds of data, barcode stripedata and pit-recorded data, can be played back. Since the stripes arerecorded in the innermost area, switching means measures the radiusposition of the optical head from the optical head stopper or from theaddress of a pit signal, and based on the result of the measurement,correctly performs switching between the two rotation control modes.

[0213] (b) Referring next to FIGS. 41 and 42, we will describe twocontrol methods for controlling the rotational speed when playing backthe barcode according to the present embodiment.

[0214]FIG. 41 shows the first rotational speed control method whereinrotational speed control is applied by detecting Tmax of a bit signal(Tmax means measuring time for a pit having the largest pit length ofvarious pit lengths).

[0215] A signal from the optical head is first subjected to waveshaping,and then the pulse spacing of the pit signal is measured by anedge-spacing measuring means 953. A t0 reference value generating means956 generates reference value information t0 whose pulse width is largerthan the pulse width 14T of the sync signal but smaller than the pulsewidth t of the barcode signal. This reference value information t0 andthe pulse width TR of the reproduced signal are compared in a comparingmeans 954; only when TR is smaller than the reference value t0 andlarger than Tmax held in a memory means 955, TR is supplied to thememory means 955 where TR is set as Tmax. By reference to this Tmax, acontroller 957 controls a motor drive circuit 958, achieving motorrotational speed control based on Tmax. In the case of the presentinvention, numerous pulses at cycles 3 to 10 μs are generated by barcodestripes, as shown in FIG. 9(a). In the case of a DVD, the sync pulsewidth is 14T, that is, 1.82 μm. On the other hand, the barcode stripewidth is 15 μm. In Tmax-based control, the barcode pulse longer than thepulse width 14T of the synch pulse will be erroneously judged anddetected as Tmax. Therefore, by removing barcode signals larger than thereference value t0 by comparison with the reference value t0, as shownin FIG. 41, it becomes possible to perform rotational speed control fornormal rotational speed during the playback of the barcode stripe area.

[0216] Next, the second rotational speed control method will bedescribed with reference to FIG. 42. This method performs rotationalspeed control by detecting Tmin (Tmin means measuring time for a pithaving the smallest pit length of various pit lengths).

[0217] In the Tmin-based control shown in FIG. 42, the pulse informationTR from the edge-spacing detecting means 953 is compared in a comparingmeans 954 a with Tmin held in a memory means 955 a; if TR<Tmin, a strobepulse occurs and the Tmin in the memory is replaced by TR.

[0218] In this case, the barcode pulse width t is 3 to 10 μm, as notedabove, while Tmin is 0.5 to 0.8 μm. As a result, if the barcode area isplayed back, the condition TR<Tmin is not satisfied since the barcodepulse width t is always greater than Tmin. That is, there is nopossibility of erroneously judging a barcode pulse as Tmin. Therefore,when the Tmin-based rotational speed control is combined with a barcodereading means 959, the effect is that rotational speed control based onTmin can be applied more stably while playing back the barcode, comparedto the Tmax-based method. Further, an oscillator clock 956 creates areference clock for demodulation in the barcode reading means 959, whiledetecting the edge spacing; this has the effect of being able todemodulate the barcode in synchronism with rotation.

[0219] (D) Next, a series of optical disk reproduction operations(playback operations) using the above control methods, etc. will bedescribed.

[0220] Referring first to FIGS. 31 and 43, a first playback method willbe described in conjunction with a method for switching between rotationphase control mode and rotational speed control mode by a mode switch963. Then, a second and a third playback method for playing back theoptical disk of the present embodiment will be described with referenceto FIGS. 38, 40, etc. The first and second playback methods hereinafterdescribed are each concerned with a case where tracking control cannotbe performed, while the third playback method is concerned with a casewhere tracking control can be performed.

[0221] At the same time that the optical head is moved to the innerportion of the disk in steps 930 b and 930 c in FIG. 31, the mode switch963 shown in FIG. 43 is switched to A. Alternatively, the mode switch963 may be switched to A when it is detected by a pickup (PU) positionsensor 962, etc. that the optical head being moved by a moving means 964has reached the inner portion of the disk.

[0222] Next, an operation when the rotational speed control mode (step930 c in FIG. 31) is entered will be described with reference to FIG.43.

[0223] A motor rotation frequency, fm, from a motor 969 and a frequency,f2, of a second oscillator 968 are compared in a second frequencycomparator 967, and a difference signal is fed to the motor drivecircuit 958 to control the motor 969, thus achieving rotational speedcontrol. In this case, since the disk is rotating with CAV, the barcodestripe can be played back.

[0224] When the barcode playback is completed in step 930 e in FIG. 31,the head is moved to an outer area by the moving means 964, and at thesame time, by a signal from the PU position sensor 962, etc., the modeswitch 963 is switched to B for rotation phase control mode.

[0225] In the rotation phase control mode, PLL control is applied to thepit signal from the optical head by a clock extracting means 960. Thefrequency f1 of a first oscillator 966 and the frequency fS of areproduced synchronization signal are compared in a first frequencycomparator 965, and a difference signal is fed to the motor drivecircuit 958. The rotation phase control mode is thus entered. Because ofPLL phase control by the pit signal, data synchronized to thesynchronization signal of f1 is played back. If the optical head weremoved to the barcode stripe area by rotation phase control, withoutswitching between rotational phase control for the motor and rotationalspeed control for the motor, phase control could not be performedbecause of the presence of the stripes, and trouble would occur, suchas, the motor running out of control or stopping, an error conditionoccurring, etc. Therefore, as shown in FIG. 43, switching to theappropriate control mode not only ensures stable playback of the barcodebut has the effect of avoiding troubles relating to motor rotation.

[0226] The second method for playing back the optical disk of thepresent embodiment will be described with reference to FIG. 38 whichshows a flowchart illustrating the operation.

[0227] The second playback method is an improved version of the firstplayback method.

[0228] More specifically, the first playback method is a method forplaying back an optical disk on which a stripe presence/absenceidentifier 937 is not defined. Since tracking is not applied in thestripe area on an optical disk of this type, it takes time todistinguish between a stripe pattern legally formed on the disk and anirregular pattern caused by scratches on the disk surface. Therefore,regardless of whether the stripes are recorded or not, the playbackprocedure has to perform a stripe reading operation first, to check thepresence or absence of stripes or whether the stripes are recorded inthe inner portion of the optical disk. This may cause a problem in thatan extra time is required before the data can be actually played back.The second playback method improves on this point.

[0229] First, as shown in FIG. 38, when an optical disk is inserted,control data is played back in step 940 a. Usually, physical featureinformation and attribute information of the optical disk are recordedas control data in a control data area. The physical feature informationincludes, for example, information indicating that the optical disk is alaminated-type disk of a two-layer, single-sided structure.

[0230] In the present invention, as shown in FIG. 30, the control datarecorded in the control data area 936 of the optical disk contains a PCAstripe presence/absence identifier 937 recorded as a pit signal.Therefore, the optical head is first moved, in step 940 n, to an outerarea where the control data is recorded. And then the optical head movesinwardly jumping across a plurality of tracks until reaching the controldata area 436. And then in step 940 a, the control data is played back.It can thus be checked whether the stripes are recorded or not. If, instep 940 b, the stripe presence/absence identifier is 0, the processproceeds to step 940 f to initiate rotation phase control for normalplayback with CLV. On the other hand, if, in step 940 b, thepresence/absence identifier 937 is 1, then the process proceeds to step940 h to check the presence or absence of a reverse-side recordidentifier 948 which indicates that the stripes are recorded on the sideopposite from the side being played back, that is, on the reverse side.If the stripes are recorded on the reverse side, the process proceeds tostep 940 i to play back the recording surface on the reverse side of theoptical disk. If the reverse side cannot be automatically played back,an indication is output for display, to urge the user to turn over thedisk. If it is determined in step 940 h that the stripes are recorded onthe side being played back, the process proceeds to step 940 c, wherethe head is moved to the stripe area 923 in the inner portion of thedisk, and in step 940 d, the control mode is switched to rotationalspeed control to play back the stripes 923 with CAY rotation. If theplayback is completed in step 940 e, then in step 940 f the control modeis switched back to rotation phase control for CLV playback and theoptical head is moved to the outer portion of the disk to play back pitsignal data.

[0231] Since the stripe presence/absence identifier 937 is recorded inthe pit area holding the control data, etc., as described above, thesecond method has the effect of being able to play back the stripes morereliably and more quickly compared to the first playback methoddescribed with reference to FIG. 31.

[0232] When the PCA area is with tracking OFF, level of the noise signalwhich is generated by the pits drops. PCA signal level remains unchangedif tracking is set OFF. Therefore, in the filtered waveform shown inFIG. 35(b), the pit signal drops, making it easier to distinguishbetween the PCA signal and the pit signal. This has the effect ofsimplifying the circuitry and reducing the error rate.

[0233] Furthermore, the provision of the stripe reverse-side recordidentifier 948 makes it possible to identify that the stripes arerecorded on the reverse side of the disk; the effect is that the barcodestripes can be played back reliably in the case of a double-sided DVDoptical disk. According to the present invention, since the stripes arerecorded penetrating through the reflective films on both sides of adisk, the stripe pattern can also be read from the reverse side of thedisk. The stripes can be played back from the reverse side of the diskby checking the stripe reverse-side identifier 948 and by playing backthe code in the reverse direction when reading the stripes. The presentinvention uses a bit string “01000110” as the synchronization code, asshown in FIG. 34(a). When played back from the reverse side, thesynchronization code is played back as “01100010”, from which it can bedetected that the barcode is being played back from the reverse side. Inthis case, by demodulating the code in reverse direction in thedemodulator 942 in the playback apparatus of FIG. 15, the barcoderecorded in penetrating fashion can be correctly played back even ifplayed back from the reverse side of a double-sided disk. The playbackapparatus of FIG. 15 will be described in more detail later.

[0234] Further, if, as shown in FIG. 30, a 300-μm wide guard-band area999, where only address information is recorded but no other data isrecorded, is provided between the PCA area 998 and the control data area936, access to the control data can be made more stable.

[0235] The guard-band area 999 will be described in more detail below.

[0236] When the optical head accesses the control data from the outerportion of the disk, the optical head moves inwardly jumping across aplurality of tracks until reaching the control data area 936. In somecases, the optical head may be moved past the destination control dataarea 936, landing at a portion further inward of the control data area.At this time, if the PCA area 998 exists directly adjacent to the innercircumference of the control data area, the optical head will lose itsown position since an address cannot be played back in the PCA area 998.It, then, becomes impossible to control the optical head.

[0237] Accordingly, when the guard-band area with a width, for example,300 μm, greater than one jump width of the optical head, is provided inthe above-noted portion, if the optical head is moved past the controldata area 936 the optical head will always land within the guard-bandarea. Then, by reading an address in the guard-band area, the opticalhead knows its own position and can thus be repositioned on thedestination control data area. In this way, the optical head can becontrolled more reliably and more quickly.

[0238] Further, as shown in FIG. 30, the control data also contains anadditional stripe data presence/absence identifier and a striperecording capacity. That is, after recording first stripes on an opticaldisk, additional stripes can be recorded in an empty, unrecorded portionof the area. The first recorded stripes will be referred to as the firstset of stripes, and the additionally recorded stripes as the second setof stripes. With this configuration, when the first set of stripes 923is already recorded by trimming, as shown in FIG. 30, the capacity ofthe available space for trimming the second set of stripes 938 can becalculated. Accordingly, when the recording apparatus of FIG. 23performs trimming to record the second set of stripes, the control dataprovides an indication of how much space is available for additionalrecording; this prevents the possibility of destroying the first set ofstripes by recording more than 360° over the area. Furthermore, as shownin FIG. 30, a gap 949 longer than one pit-signal frame length isprovided between the first set of stripes 923 and the second set ofstripes 938; this serves to prevent the previously recorded trimmingdata from being destroyed.

[0239] Moreover, as shown in FIG. 34(b) to be described later, atrimming count identifier 947 is recorded in a synchronization codearea. This identifier is used to distinguish between the first set ofstripes and the second set of stripes. Without this identifier,discrimination between the first set of stripes 923 and the second setof stripes 938 in FIG. 30 would become impossible.

[0240] Finally, the third playback method will be described withreference to FIG. 40.

[0241] When the duty ratio of the stripe on the optical disk, that is,its area ratio, is low, almost correct tracking can be maintained in thestripe area, as shown in FIG. 32. Therefore, the address information inthe address area 944 at the same radius position of the disk can beplayed back. This has the effect of quickening the disk rise time afterdisk insertion since the address can be played back while playing backthe stripes without changing the optical head position.

[0242] In this case, the address area, an area where no stripes arerecorded, should be formed continuously along a length longer than oneframe in the same radium portion of the disk.

[0243] The operation steps for this method will be described withreference to FIG. 40.

[0244] When a disk is inserted, the optical head is moved to the innercircumferential portion in step 947 a. If no tracking is achieved instep 947 n, the tracking mode is switched from phase control topush-pull mode in step 947 p. In step 947 b, rotational speed control(CAV control) is performed to play back address information. If anaddress cannot be played back in step 947 c, the process proceeds tostep 947 i to move the optical head inward to play back the PCA stripes.If an address can be played back from an empty portion of the PCA area(a portion not overwritten), the process proceeds to step 947 e where,based on the address, the optical head is moved in a radial direction tothe address area where stripes are recorded. In step 947 q, the presenceor absence of PCA stripes is checked If it is judged that there are noPCA stripes, the process proceeds to step 947 r to try to read a PCAflag in the control data. Then, in step 947 s, the presence or absenceof the PCA flag is checked. If the presence of the PCA flag is detected,the process returns to step 947 c: otherwise, the process jumps to step947 m.

[0245] On the other hand, if it is judged in step 947 q that there arePCA stripes, the process proceeds to step 947 f to play back the PCAstripes. When the playback is completed in step 947 g, then the mode isswitched to rotation phase control and the optical head is moved to theouter area to play back a pit signal. In step 947 t, the PCA flag in thecontrol data is read; if there is no PCA flag, an error message isissued in step 947 k, and the process returns to 947 m to continue theprocess.

[0246] (E) Next, manufacturing techniques for implementing the opticaldisk barcode forming method of the invention will be described infurther detail. A barcode playback apparatus will also be describedbriefly.

[0247] (a) First, manufacturing techniques for implementing the barcoderecording method will be described.

[0248] In the case of the barcode recording method previously explainedwith reference to FIG. 28, the minimum emitting-pulse spacing is 1t;therefore, a laser with a pulse repetition period of fC=1/f_(L) isrequired, where f_(L) is the frequency of the laser. In this case, thenumber, f_(L)/2, of barcode bars can be recorded per second. However, ifa beam deflector 931 is used, as shown in FIG. 29, a minimumemitting-pulse spacing of 2t is allowed, so that the pulse repetitionperiod is f_(L)=1/2t. which means that the laser frequency can bereduced by a factor of 2. This also means that, when a laser of the samefrequency is used, the number of barcode bars that can be recorded persecond can be doubled to f_(L) by using the beam deflector 931. This hasthe effect of reducing the productive tact (processing tact) by a factorof 2.

[0249] The operation of a double-efficiency apparatus (referred to as“switch recording”) using the beam deflector 931 will be described belowwith reference to FIG. 29, focusing on differences from theconfiguration of FIG. 28.

[0250] The beam deflector 931, formed from an acousto-optical modulatoror the like, is supplied with a deflection signal for switching the beambetween a main beam 945 and a sub-beam 946; when the deflection signalis ON, the beam is switched to the sub-beam 946 which is passed througha sub-slit 932 b and forms a sub-stripe 934. More specifically, for data“0” a normal stripe 933 is formed; only when recording data “1” is thedeflection signal set to ON, as shown in FIG. 29(b), in response towhich the beam deflector 931 switches the beam to the sub-beam 946 torecord a stripe at the position of the sub-stripe 934. In this manner,stripes 933 a and 933 b, each for “0”, and a stripe 934 a for “1”, asshown in part (b), are formed on the disk. In this configuration, sincea laser pulse need only be produced at intervals of 2t, a laser with afrequency half that required in the configuration of FIG. 28 can beused. In other words, when a laser of the same frequency is used, sincethe stripes can be formed at twice the clock frequency, this has theeffect of increasing the productivity by a factor of 2, as alreadydescribed.

[0251] Next, referring to the data structure of the synchronization codeshown in FIG. 34, a format suitable for the switch recording explainedwith reference to FIG. 29 will be described below. The synchronizationcode data structure also constitutes a technique for improvingproductivity.

[0252] As shown in FIG. 34(a), a fixed pattern of “01000110” is usedhere. Conventionally, a bit string consisting of the same number of 0sand 1s, such as “01000111”, is used, but the present inventiondeliberately avoids this and uses the illustrated data structure for thereason explained below.

[0253] First, to achieve the switch recording of FIG. 29, provisionsmust be made so that two or more pulses will not occur within one timeslot, that is, within 1T interval. Switch recording is possible in thedata area because data is recorded there with a PE-RZ code, as shown inFIG. 33(a). However, in the case of the synchronization code of FIG.34(a), since irregular channel bits are arranged, with the usual methodtwo pulses may occur within 1T, in which case the switch recording ofthe invention is not possible. To address this problem, the inventionemploys, for example, the bit pattern “01000110” as shown in FIG. 37.With this bit pattern, in T1 a pulse occurs for the “1” on the right. inT2 no pulses occur, in T3 a pulse occurs for the “1” on the right, andin T4 a pulse occurs for the “1” on the left; in this way, two or morepulses cannot occur within one time slot. Thus, the synchronization codestructure of the invention has the effect of achieving switch recording,increasing the production rate by a factor of 2.

[0254] (b) Next, referring to FIG. 15, a brief description will be givenof a playback apparatus for playing back the barcode recorded on anoptical disk by the above method. The description will also touch onproductivity increases.

[0255]FIG. 15 is a block diagram of the playback apparatus alreadydescribed in (I).

[0256] In the first-half part (I), the apparatus has been described asan apparatus for reading the position of a marking formed on thereflective film of an optical disk, but hereinafter, the apparatus ofFIG. 15 will be described as a barcode reading apparatus, that is, aplayback apparatus.

[0257] An explanation will be given again referring to FIG. 15, thistime focusing on the demodulation operation. First, high-frequencycomponents generated by pits are removed by a low-pass filter (LPFfilter) 94 from a stripe signal output.

[0258] In the case of a DVD, there is a possibility that a hmaximum 14Tsignal may be played back, where T=0.13 μm. In this case, it has beenconfirmed by experiment, a stripe signal and a high-frequency componentgenerated by a pit can be separated by using the second-order orthird-order Chevihov low-pass filter shown in FIG. 35(a). That is, theuse of a second- or higher-order LPF has the effect of being able toseparate a pit signal and a barcode signal, thus ensuring stableplayback of a barcode. FIG. 35(b) shows the simulation waveform which isgenerated when the signal of the maximum 14T pit length is recordedcontinuously.

[0259] In this way, by using the second- or higher-order LPF 943, thestripe playback signal can be output after substantially removing thepit playback signal; this ensures reliable demodulation of stripesignals. However, if the width of a stripe signal thus demodulated (thestripe signal width shown as 15 μm in FIG. 36(b)) is smaller than thesampling interval width tm (see FIG. 36(c)) of a microcomputer, thestripe signal may not be measured accurately. For example, of the stripesignals shown in FIG. 36(b), the stripe signal on the left is locatedinside of the microcomputer sampling interval width, and therefore, isnot detected. To avoid this, a stripe signal obtained by reading astripe is waveshaped using a flip-flop circuit so that the signal widthbecomes greater than the microcomputer sampling interval width tm, asshown in FIG. 36(d). FIG. 36(d) shows a waveform after the stripe signalwidth was increased to a width Bw. The waveshaped signal is thendetected with sampling pulses (see FIG. 36(c)) from the microcomputer.This ensures accurate measurement of the stripe signal.

[0260] Referring back to FIG. 15. a further description will be given.Digital data is demodulated by the PE-RZ demodulator 942 in the abovemanner. The data is then fed to an ECC decoder 928 for error correction.That is, deinterleaving is performed in a deinterleaver 928 a, andReed-Solomon code computation is performed in an RS decoder 928 b forerror correction.

[0261] A brief description will now be given in relation to productivetact.

[0262]FIG. 33(a) shows the data structure after the barcode is ECCencoded according to the present embodiment. FIG. 33(b) shows the datastructure after ECC encoding when n=1 according to the presentembodiment. FIG. 33(c) shows an ECC error-correction capabilityaccording to the present embodiment.

[0263] In the present invention, the interleaving and Reed-Solomonerror-correction coding shown in the data structure of FIG. 33(a) areperformed using the ECC encoder 927 shown in FIG. 1 whenrecording-stripes on an optical disk. With this error-correction method,a read error occurs in only one disk out of 10⁷=10 million optical disksunder the condition of that Byte error rate of 10⁻⁴ occurs, as shown inFIG. 33(c). In this data structure, to reduce the code data length thesame sync code is assigned to four rows, reducing the number of synccodes by a factor of 4 and thus increasing efficiency. With furtherreference to FIG. 33, the scalability of the data structure will bedescribed. In the present invention, the recording capacity can bevaried freely, for example, within a range of 12B (12 Byte) to 188B inincrements of 16B, as shown in the example of FIG. 34(c). That is, n canbe changed within a range of n=1 to n=12, as shown in FIG. 33(c).

[0264] As shown in FIG. 33(b) and FIG. 49(a), for example, in the datastructure when n=1, there are only four data rows 951 a, 951 b, 951 c,and 951 d, followed by ECC rows 952 a, 952 b, 952 c, and 952 d. FIG.49(a) is a diagram showing FIG. 33(b) in further detail. The data row951 constitutes EDC of 4B. FIG. 49(b) shows this in an equivalent form.Error-correction encoding computation is performed, assuming that datarows from 951 e to 951 z all contain 0s. Mathematical equations for EDCand ECC computations are shown in FIGS. 49(c) and 49(d), respectively.In this way, the data is ECC-encoded by the ECC encoder 927 in therecording apparatus of FIG. 1 and recorded as a barcode on the disk.When n=1, data of 12B is recorded over an angle of 51 degrees on thedisk. Likewise, when n=2, data of 18B can be recorded; when n=12, dataof 271B can be recorded over an angle of 336 degrees on the disk. In thepresent invention, by encoding and decoding the data using the EDC andECC computation equations shown in FIGS. 49(c) and 49(d), when the dataamount is smaller than 188B, the computation is performed assuming allremaining bits are 0s, so that the data is stored with a small recordingcapacity. This serves to shorten the productive tact. When performinglaser trimming, as in the present invention, the above-describedscalability has a significant meaning. More specifically, whenperforming laser trimming at a factory, it is important to shorten theproductive tact. With a slow-speed apparatus which trims one stripe at atime, it will take more than 10 seconds to record a few thousand stripesto the full capacity. The time required for disk production is 4 secondsper disk; if full-capacity recording has to be done, the productive tactincreases. On the other hand, for the moment, disk ID number will be amain application area of the present invention; in this application, thePCA area capacity can be as low as 10B. If 271B are recorded when only10B need to be written, the laser processing time will increase by afactor of 6, leading to a production cost increase. The scalabilitymethod of the present invention achieves reductions in production costand time.

[0265] In the playback apparatus shown in FIG. 15, when n=1 as in FIG.33(b), for example, the ECC decoder 928 performs the EDC and ECCerror-correction computations shown in FIGS. 49(c) and 49(d), assumingthat the data rows 951 e to 951 z all contain 0s; the effect of this isthat data of 12 to 271B can be corrected for errors by using the sameprogram. In this case, the number of program steps decreases, permittingthe use of a small-capacity ROM in the microcomputer.

[0266] Furthermore, the pulse width reproduced from each stripe width ismade less than ½ of one pulse period, as shown in FIG. 36. Since thereare three difference pulse spacings, 1T, 2T, and 3T, the ratio of thesum of all the stripe areas in one track to the total area of the trackis less than ⅓. With this arrangement, in the case of a disk of standardreflectivity of 70% the reflectivity of the stripe area is ⅔ of that,i.e., about 50%. Since this value is enough for focus control, the PCAarea can be played back on a conventional ROM disk player.

[0267] (F) Next, an example of the above-described barcode encryption(including digital signature) will be described with reference todrawings, followed by a description of another application example ofthe barcode.

[0268] (a) First, the barcode encryption process and playback processwill be described by way of example with reference to FIG. 45.

[0269] As shown in FIG. 45, an ID number 4504 unique to each individualoptical disk is generated by an ID generator 4502. At the same time, anID signature section 4503 applies a digital signature to the ID numberby using a specific secret key corresponding to a specific public key,and the thus applied digital signature 4505 and its associated ID number4504 are sent together as a series of data to a press factory 4501. Thisdigital signature is applied to the ID number encrypted in an encryptionencoder 4508 using a secret key of a public key encryption function. Thepublic key corresponding to this secret key is sent to the press factory4501. At the press factory 4501, the ID number and its correspondingdigital signature 4505 are recorded as a barcode in the PCA area of anoptical disk 4506 by using a PCA writer 4507. The public key isprerecorded on the master disk, that is, in a pit portion of the disk.When the thus manufactured optical disk 4506 is loaded into a playbackapparatus (player) 4509, the public key is read from the pit portion,and the ID number and the digital signature appended to it are read fromthe PCA area and decrypted with the public key. The result of thedecryption is passed to a verification section 4511; if the digitalsignature data is found legitimate as the result of the verification,the playback operation of the optical disk is allowed to continue. Ifthe digital signature data is found illegitimate as the result of theverification, the operation is stopped. Here, if the digital signaturedata is recorded in the PCA area together with the plaintext of the ID,the result of the decryption is checked against the plaintext of the IDto see if they match. If the digital signature data only is recorded inthe PCA area, an error check is performed for verification When the datais encrypted with public key cipher, as described above, only thesoftware manufacturer that has the secret key can issue a new ID number.Accordingly, if pirated disks were made, the encrypted ID of the samenumber would be recorded in the PCA area of every disk; therefore, theuse of such pirated disks would be greatly limited. The reason is that,in such cases, the illegal use of the software having the same numbercan be prevented by applying network protection. Needless to say, theabove method described with reference to FIG. 45 can also be used in theInternet.

[0270] (b) Another application example of the barcode will be describedwith reference to FIG. 46 as another mode of embodiment.

[0271] This mode of embodiment is concerned with an example in which anencryption key to be used during communication is recorded as theabove-described barcode in the PCA area.

[0272] As shown in FIG. 46, a press factory 4601 keeps each ID numberand its corresponding encryption key, a public key of a public keyencryption function, in the form of a table 4602. At the press factory4601, an ID number and its corresponding public key are recorded in thePCA area 4605 of an optical disk 4604 by using a PCA writer 4603.

[0273] Next, we will describe how the user who purchased the thuscompleted optical disk 4604 can play it back on his player. Consider,for example, a case in which he desires to watch movie software recordedon the optical disk. Before the user can play back the movie containedon the optical disk 4604, he has to arrange for payment to a systemmanagement center 4610 and have a password issued to enable playback.

[0274] First, the user sets the optical disk 4604. With communicationsoftware run on a personal computer 4606, the PCA area, etc. are playedback and the public key is read out. When the user enters his creditcard number and personal code number, an encryption encoder 4607encrypts the entered data with the public key, and the encrypted data istransmitted to the system management center 4610 by using thecommunications channel 4620. At the system management center 4610, acommunication section 4611 reads the ID number in plaintext from thereceived data, and decrypts the received data by retrieving a secret keycorresponding to the ID number from an encryption key table 4612. Thatis, the system management center 4610 keeps the encryption key table4612 containing mapping information for each ID number and a secret keycorresponding to the public key. Based on the user's credit card numberand personal code number retrieved from the decrypted data, the systemmanagement center 4610 charges the user, and at the same times, issues apassword to the user. This password corresponds to the disk ID anduser-specified movie or computer software contained on the disk 4604.Using the password thus issued. the user can play back the desired movieor install the desired computer software.

[0275] Since the public key can be prerecorded as a barcode on theoptical disk, this mode of embodiment has the effect of saving time andlabor taken in a previous system that required the system managementcenter to send the public key to the user separately. Furthermore, evenif the communication key (public key) is delivered to a press factorywhere no particular security measures are implemented, security can bemaintained. Furthermore, since a different public key is used for eachindividual disk, if security of one particular disk, that is, one user,is broken, the security of other users can be protected. Furthermore,using different public keys for different disks has the effect ofreducing the possibility of a third party placing an illegal order. Ifthe communication public key were recorded on the master disk, it wouldnot be possible to prevent a third party from placing an illegal order.In the example of FIG. 46, a public key is used as the communicationkey, but it will be appreciated that similar effects can be obtained ifa secret key is used. In this case, however, the security level is alittle lower than when a public key is used. Needless to say, the methoddescribed with reference to FIG. 46 can also be used in the Internet.

[0276] Referring to FIG. 22, we will now describe in detail a method ofdescrambling and decrypting data using a password via the networkdescribed with reference to FIG. 46. In the flowchart of FIG. 22, firstin step 901 a the software on the disk checks the scramble identifier tosee if the identifier is ON. If the answer is NO, the process proceedsto step 901 b; if the software is not scrambled, the installation isallowed to continue. On the other hand, if the answer is YES, it ischecked in step 901 b whether the software is scrambled or not; if YES,a connection is made to the personal computer network in step 901 c,which is followed by step 901 d where the-user enters the user ID andsoftware ID. If, in step 901 c, there is a drive ID, then in step 901 fthe drive ID data is transmitted to the password issuing center. Afterconfirming payment, in step 901 g the password issuing center performsencryption computation on the drive ID and software ID by using a subsecret key, and generates a password which is transmitted to the user.The process then proceeds to step 901 h. The personal computer at theuser end computes the password by a sub public key and compares it withthe drive ID. If the result is OK, the process proceeds to step 901 nwhere the software scramble or encryption is unlocked.

[0277] Turning back to step 901 e, if the answer is NO, then in step 901h it is checked whether there is a disk ID. If there is a disk ID, thenin step 901 i the disk ID data is transmitted to the password issuingcenter. After confirming payment, in step 901 j the password issuingcenter performs encryption computation on the disk ID and software ID byusing a sub secret key, and generates a password which is transmitted tothe user. In step 901 m, the personal computer at the user end computesthe password by a sub public key and compares it with the drive ID. Ifthe result is OK, the process proceeds to step 901 n where the softwarescramble is unlocked.

[0278] In this way, by communicating with the password issuing centervia the network by using a disk ID, the software scramble or encryptionon the disk can be unlocked. In the case of the disk ID of the presentinvention, since the ID varies from disk to disk, the password is alsodifferent; this has the effect of enhancing security. In FIG. 22,ciphertext communication is omitted, but by encrypting data using apublic key recorded in the PCA area, such as shown in FIG. 46, duringthe communication performed in steps 901 i and 901 j, data securityduring communication can be further enhanced. This has the effect ofensuring safe transmission of personal billing information via acommunication means such as the Internet where the security level islow.

[0279] We will finish here the descriptions of the first-half part (I)and the second-half part (II), and now proceed to a description ofappertaining matters relating to the process from optical diskmanufacturing to the playback operation of the player.

[0280] (A) A low reflectivity portion address table, which is a positioninformation list for the low reflectivity portion, will be explained.

[0281] (a) Laser markings are formed at random in the anti-piracy markformation process at the factory. No laser markings formed in thismanner can be identical in physical feature. In the next process step,the low reflectivity portion 584 formed on each disk is measured with aresolution of 0.13 μm in the case of a DVD, to construct a lowreflectivity portion address table 609 as shown in FIG. 13(a). Here,FIG. 13(a) is a diagram showing a low reflectivity portion addresstable, etc. for a legitimate CD manufactured in accordance with thepresent embodiment, and FIG. 13(b) is concerned with an illegallyduplicated CD. The low reflectivity portion address table 609 isencrypted using a one-direction function such as the one shown in FIG.18, and in the second reflective-layer forming step, a series of lowreflectivity portions 584 c to 584 e, where the reflective layer isremoved, is recorded in a barcode-like pattern on the innermost portionof the disk, as shown in FIG. 2. FIG. 18 is a flowchart illustrating adisk check procedure by the one-way function used for the encryption. Asshown in FIG. 13, the legitimate CD and the illegally duplicated CD havethe low reflectivity portion address tables 609 and 609 x, respectively,which are substantially different from each other. One factor resultingin this difference is that laser markings identical in physical featurecannot be made, as earlier noted. Another factor is that the sectoraddress preassigned to the disk is different if the master disk isdifferent.

[0282] Referring now to FIG. 13, we will describe how the markingposition information differs between the legitimate disk and pirateddisk. The figure shows an example in which the above two factors arecombined. In the example shown, two markings are formed on one disk. Inthe case of the legitimate CD, the first marking of mark number 1 islocated at the 262nd clock position from the start point of the sectorof logical address A1, as shown in the address table 609. In the case ofa DVD, one clock is equivalent to 0.13 μm, and the measurement is madewith this accuracy. On the other hand, in the case of the pirated CD,the first marking is located at the 81st clock position in the sector ofaddress A2, as shown in the address table 609 x. By detecting thisdifference of the first marking position between the legitimate disk andpirated disk, the pirated disk can be distinguished. Likewise, theposition of the second marking is also different. To make the positioninformation match that of the legitimate disk, the reflective film atthe 262nd position in the sector of address A1 must be formed with anaccuracy of one clock unit, i.e., 0.13 μm; otherwise, the pirated diskcannot be run.

[0283] In the example of FIG. 16, the legitimate disk and illegallyduplicated disk have low reflectivity portion address tables 609 and 609x respectively, where values are different as shown in FIG. 17. In thecase of the legitimate disk, in the track following the mark 1 the startand end positions are m+14 and m+267, respectively, as shown in FIG.16(8), whereas in the case of the illegally duplicated disk these. arem+24 and m+277, respectively, as shown in FIG. 16(9). Therefore, thecorresponding values in the low reflectivity portion address tables 609and 609 x are different, as shown in FIG. 17, thus making it possible todistinguish the duplicated disk. If an illegal manufacturer desires tomake a copy of the disk having the low reflectivity portion addresstable 609, they will have to perform a precise laser trimming operationwith the resolution of the reproduced clock signal as shown in FIG.16(8).

[0284] As shown in FIG. 20(5) showing the waveform of a PLL reproducedclock signal out of reproduced optical signals, in the case of a DVDdisk the period T of one reproduced clock pulse, when converted to adistance on the disk, that is, one pulse spacing on the disk, is 0.13μm. Accordingly, to make an illegal copy, the reflective film will haveto be removed with a submicron resolution of 0.1 μm. It is true thatwhen an optical head designed for an optical disk is used, a recordingcan be made on a recording film such as a CD-R with a submicronresolution. But in this case, the reproduced waveform will be as shownin FIG. 9(c), and the distinct waveform 824 as shown in FIG. 9(a) cannotbe obtained unless the reflective film is removed.

[0285] (b) A first method of achieving mass production of pirated disksby removing the reflective film may be by laser trimming using a highoutput laser such as a YAG laser. At the present state of technology,even the most highly accurate machining laser trimming can only achievea processing accuracy of a few microns. In the laser trimming forsemiconductor mask corrections, it is said that 1 μm is the limit of theprocessing accuracy. This means that it is difficult to achieve aprocessing accuracy of 0.1 μm at the mass production level.

[0286] (c) As a second method, X-ray exposure equipment for processingsemiconductor masks for VLSIs and ion beam processing equipment areknown at the present time as equipment that can achieve a processingaccuracy of the order of submicrons, but such equipment is veryexpensive and furthermore, it takes much time to process one piece ofdisk, and if each disk were processed using such equipment, the cost perdisk would be very high. At the present time, therefore, the cost wouldbecome higher than the retail price of most legitimate disks, so thatmaking pirated disks would not pay and meaningless.

[0287] (d) As described above, with the first method that involves lasertrimming, it is difficult to process with a submicron accuracy, andtherefore, it is difficult to mass produce pirated disks. On the otherhand, with the second method using the submicron processing technologysuch as X-ray exposure, the cost per disk is so high that making pirateddisks is meaningless from an economic point of view. Accordingly, makingillegal copies can be prevented until some day in the future whenlow-cost submicron processing technology for mass production becomespractical. Since practical implementation of such technology will bemany years into the future, production of pirated disks can beprevented. In the case of a two-layer disk with a low reflectivityportion formed on each layer as shown in FIG. 33, an illegallyduplicated disk cannot be manufactured unless the pits on top and bottomare aligned with good accuracy when laminating, and this enhances theeffectiveness in preventing piracy.

[0288] (B) Next, we will describe how the arrangement angle of the lowreflectivity portion on the disk can be specified.

[0289] In the present invention, sufficient effectiveness in piracyprevention is provided by the reflective-layer level mechanism, that is,by the low reflective marking alone. In this case, the prevention iseffective even if the master disk is a duplicate. However, theeffectiveness can be enhanced by combining it with the piracy preventiontechnique at the master disk level. If the arrangement angle of the lowreflectivity portion on the disk is specified as shown in Table 532 aand Table 609 in FIG. 13(a), an illegal manufacturer would have toaccurately duplicate even the arrangement angle of each pit on themaster disk. This would increase the cost of pirated disks and henceenhance the capability to deter piracy.

[0290] (C) A further description will be given of the operation ofreading the nonreflective optical marking portion of the two-disklaminated optical disk, focusing on points that were not touched on inthe foregoing description of the operating principle.

[0291] That is, as shown in FIG. 16, the start position address number,frame number, and clock number can be measured accurately with aresolution of 1 T unit, that is, with a resolution of 0.13 μm in thecase of the DVD standard, by using a conventional player, thereby toaccurately measure the optical mark of the present invention. FIGS. 20and 21 show the optical mark address reading method of FIG. 16.Explanation of signals (1), (2), (3), (4), and (5) in FIGS. 20 and 21will not be given here since the operating principle is the same as thatshown in FIG. 16.

[0292] The correspondence between FIG. 16, which illustrates theprinciple of the detection operation for detecting the position of a lowreflectivity portion on a CD, and FIGS. 20 and 21, which are concernedwith a DVD, is given below.

[0293]FIG. 16(5) corresponds to FIGS. 20(1) and 21(1). The reproducedclock signal in FIG. 16(6) corresponds to that shown in FIGS 20(5) and21(5). Address 603 in FIG. 16(7) corresponds to that shown in FIGS.20(2) and 21(2).

[0294] Frame synch 604 in FIG. 16(7) corresponds to that shown in FIGS.20(4) and 21(4). Starting clock number 605 a in FIG. 16(8) correspondsto reproduced channel clock number in FIG. 20(6). Instead of the endclock number 606 in FIG. 16(7), in FIGS. 20(7) and 21(7) data iscompressed using a 6-bit marking length.

[0295] As illustrated, the detection operation is fundamentally the samebetween CD and DVD. A first difference is that a 1-bit mark layeridentifier 603 a as shown in FIG. 20(7) is included for identifyingwhether the low reflectivity portion is of the one-layer type ortwo-layer type. The two-layer DVD structure provides a greateranti-piracy effect, as previously described. A second difference is thatsince the line recording density is nearly two times as high, 1 T of thereproduced clock is as short as 0.13 μm, which increases the resolutionfor the detection of the position information and thus provides agreater anti-piracy effect.

[0296] Shown in FIG. 20 is the signal from the first layer in atwo-layer optical disk having two reflective layers. The signal (1)shows the condition when the start position of an optical mark on thefirst layer is detected. FIG. 21 shows the condition of the signal fromthe second layer.

[0297] To read the second layer, a first/second layer switching section827 in FIG. 15 sends a switching signal to a focus control section 828which then controls a focus driving section 829 to switch the focus fromthe first layer to the second layer. From FIG. 20. it is found that themark is in address (n), and by counting the frame synchronizing signal(4) using a counter, it is found that the mark is in frame 4. Fromsignal (5), the PLL reproduced clock number is found. and the opticalmarking position data as shown by the signal (6) is obtained. Using thisposition data, the optical mark can be measured with a resolution of0.13 μm on a conventional consumer DVD player.

[0298] (D) Additional matters relating to the two-disk laminated opticaldisk will be further described below.

[0299]FIG. 21 shows address position information pertaining to theoptical marking formed on the second layer. Since laser light penetratesthe first and second layers through the same hole, as shown in theprocess step (6) in FIG. 7, the nonreflective portion 815 formed on thefirst reflective layer 802 and the nonreflective portion 826 formed onthe second reflective layer 825 are identical in shape. This is depictedin the perspective view of FIG. 47. In the present invention, after thetransparent substrate 801 and the second substrate 803 are laminatedtogether, laser light is applied penetrating through to the second layerto form an identical mark thereon In this case, since coordinatearrangements of pits are different between the first and second layers,and since the positional relationship between the first and secondlayers is random when laminating them together, the pit positions wherethe mark is formed are different between the first and second layers,and entirely different position information is obtained from each layer.These two kinds of position information are encrypted to produce ananti-piracy disk. If it is attempted to duplicate this disk illegally,the optical marks on the two layers would have to be aligned with aresolution of about 0.13 μm. As previously described, at the presentstate of technology it is not possible to duplicate the disk by aligningthe optical marks with the pits with an accuracy of 0.13 μm, that is,with an accuracy of the order of 0.1 μm, but there is a possibility thatmass production technology may be commercially implemented in the futurethat enables large quantities of single-layer disks to be trimmed with aprocessing accuracy of 0.1 μm at low cost. Even in that case, since thetop and bottom disks are trimmed simultaneously in the case of thetwo-layer laminated disk 800, the two disks must be laminated togetherwith the pit locations and optical marks aligned with an accuracy of afew microns. However, it is next to impossible to laminate the diskswith this accuracy because of the temperature coefficient, etc. of thepolycarbonate substrate. When optical marks were formed by applyinglaser light penetrating through the two-layer disk 800, the resultinganti-piracy mark is extremely difficult to duplicate. This provides agreater anti-piracy effect. The optical disk with an anti-piracymechanism is thus completed. For piracy prevention applications, incases where the disk process and laser cut process are inseparable as inthe case of the single-plate type, the encryption process, which is anintegral part of the laser cut process, and processing involving asecret encryption key have to be performed at the disk manufacturingfactory. This means that in the case of the single-plate type the secretencryption key maintained in the software company have to be deliveredto the disk manufacturing factory. This greatly reduces the security ofencryption. On the other hand, according to the method involving laserprocessing of laminated disks, which constitutes one aspect of theinvention, the laser trimming process can be completely separated fromthe disk manufacturing process. Therefore, laser trimming and encryptionoperations can be performed at a factory of the software maker. Sincethe secret encryption key that the software maker keeps need not bedelivered to the disk manufacturing factory, the secret key forencryption can be kept in the safe custody of the software maker. Thisgreatly increases the security of encryption.

[0300] (E) As described above, in the present invention, a legitimatemanufacturer can make a legitimate disk by processing the disk using ageneral-purpose laser trimming apparatus having a processing accuracy ofseveral tens of microns. Though a measuring accuracy of 0.13 μm isrequired, this can be achieved by conventional circuitry contained in aconsumer DVD player. By encrypting the measured result with a secretencryption key, a legitimate disk can be manufactured. That is, thelegitimate manufacturer need only have a secret key and a measuringapparatus with a measuring accuracy of 0.13 μm, while the requiredprocessing accuracy is two or three orders of magnitude lower, that is,several tens of microns. This means that a convectional laser processingapparatus can be used. On the other hand, an illegal manufacturer, whodoes not have a secret key, will have to directly copy the encryptedinformation recorded on the legitimate disk. This means that a physicalmark corresponding to the encrypted position information, that is, theposition information on the legitimate disk, must be formed with aprocessing accuracy of 0.13 μm. That is, the low reflective mark has tobe formed using a processing apparatus having a processing accuracy twoorders of magnitude higher than that of the processing apparatus used bythe legitimate manufacturer. Volume production with an accuracy higherby two orders of magnitude, i.e., with an accuracy of 0.1 μm, isdifficult both technically and economically, even in the foreseeablefuture. This means that production of pirated disks can be preventedduring the life of the DVD standard. One point of the invention is toexploit the fact that the measuring accuracy is generally a few ordersof magnitude higher than the processing accuracy.

[0301] In the case of CLV, the above method exploits the fact that theaddress coordinate arrangement differs from one master disk to another,as previously noted. FIG. 48 shows the result of the measurement ofaddress locations on actual CDs. Generally, there are two types ofmaster disk, one recorded by rotating a motor at a constant rotationalspeed, i.e., with a constant angular velocity (CAV), and the otherrecorded by rotating a disk with a constant linear velocity (CLV). Inthe case of a CAV disk, since a logical address is located on apredetermined angular position on the disk, the logical address and itsphysical angular position on the disk are exactly the same no matter howmany master disks are made. On the other band, in the case of a CLVdisk; since only the linear velocity is controlled, the angular positionof the logical address on the master disk is random. As can be seen fromthe result of the measurement of logical address locations on actual CDsin FIG. 48, the tracking pitch, start point and linear velocity varyslightly from disk to disk even if exactly the same data is recordedusing the same mastering apparatus, and these errors accumulate,resulting in different physical locations. In FIG. 48, the locations ofeach logical address on a first master disk are indicated by whitecircles, and the locations on second and third master disks areindicated by black circles and triangles, respectively. As can be seen,the physical locations of the logical addresses vary each time themaster disk is made. FIG. 17 shows the low reflectivity portion addresstables for a legitimate disk and an illegally duplicated disk forcomparison.

[0302] The method of piracy prevention at the master disk level has beendescribed above. This is, when master disks of CLV recording, such as aCD or DVD, are made from the same logic data by using a masteringapparatus, as shown in FIG. 48, the physical location of each pit on thedisk varies between master disks, that is, between the legitimate diskand pirated disk. This method distinguishes a pirated disk from alegitimate disk by taking advantage of this characteristic. The piracyprevention technology at the master disk level can prevent pirated disksat the logic level made by simply copying data only from the legitimatedisk. However, recent years have seen the emergence of piratemanufacturers equipped with more advanced technologies, who can make amaster disk replica identical in physical feature to a legitimate diskby melting the polycarbonate substrate of the legitimate disk. In thiscase, the piracy prevention method at the master disk level is defeated.To prevent this new threat of pirated disk production, the presentinvention has devised the piracy prevention method at the reflectivelayer level wherein a marking is formed on a reflective film.

[0303] According to the method of the present invention, the marking isformed on each disk pressed from a master disk, even if disks arepressed from the master disk, by removing a portion of the reflectivefilm in the reflective film formation process. As a result, the positionand shape of the resulting low reflective marking is different from onedisk to another. In a usual process, it is next to impossible topartially remove the reflective film with an accuracy of submicrons.This serves to enhance the effectiveness in preventing duplication sinceduplicating the disk of the invention does not justify the cost.

[0304]FIG. 19 shows a flowchart for detecting a duplicated CD by usingthe low reflectivity portion address table. The delay time needed todetect the optical mark varies only slightly due to the optical head andcircuit designs of the reproduction apparatus used. This of the delaytime TD circuit can be predicted at the design stage or at the time ofmass production. The optical mark position information is obtained bymeasuring the number of clocks, that is, the time, from the framesynchronizing signal. Due to the effect of the circuit delay time, anerror may be caused to detected data of the optical mark positioninformation. As a result, a legitimate disk may be erroneously judged asbeing a pirated disk, inconveniencing a legitimate user. A measure toreduce the effect of the circuit delay time TD will be described below.Further, a scratch made on a disk after purchase may cause aninterruption in the reproduced clock signal, causing an error of a fewclocks in the measurement of the optical mark position information. Toaddress this problem, a tolerance 866 and a pass count 867, shown inFIG. 20, are recorded on a disk, and while allowing a certain degree oftolerance on the measured value according to the actual situation at thetime of reproduction. the reproduction operation is permitted when thepass count 867 is reached; the margin allowed for an error due to asurface scratch on the disk can be controlled by the copyright ownerprior to the shipment of the disk. This will be described with referenceto FIG. 19.

[0305] In FIG. 19, the disk is reproduced in step 865 a to recover theencrypted position information from the barcode recording portion or pitrecording portion of the present invention. In step 865 b, decryption orsignature verification is performed, and in step 865 c, a list ofoptical mark position information is recovered. Next, if the delay timeTD of a reproduction circuit is stored in the circuit delay time storingsection 608 a in the reproduction apparatus of FIG. 15, TD is read outin step 865 h and the process proceeds to step 865 x. If TD is notstored in the reproduction apparatus, or if a measurement instruction isrecorded on the disk, the process proceeds to step 865 d to enter areference delay time measurement routine. When address Ns−1 is detected,the start position of the next address Ns is found. The framesynchronizing signal and the reproduced clock are counted, and in step865 f, the reference optical mark is detected. In step 865 g, thecircuit delay time TD is measured and stored. This operation is the sameas the operation to be described later with reference to FIG. 16(7). Instep 865 x, the optical mark located inside address Nm is measured. Insteps 865 i, 865 j, 865 k, and 865 m, the optical mark positioninformation is detected with a resolution of one clock unit, as in steps865 d, 865 y, 865 f, and 865 y. Next, in step 865 n, a pirated diskdetection routine is entered. First, the circuit delay time TD iscorrected. In step 865 p, the tolerance 866, i.e., tA, and pass count867 recorded on the disk, as shown in FIG. 20, are read to check whetheror not the position information measured in step 865 g falls within thetolerance tA. If the result is OK in step 865 r, then in step 865 s itis checked whether the checked mark count has reached the pass count. Ifthe result is OK, then in step 865 u the disk is judged as being alegitimate disk and reproduction is permitted. If the pass count is notreached yet, the process returns to step 865 z. If the result is NO instep 865 r, then it is checked in step 865 f whether the error detectioncount is smaller than NA, and only when the result is OK, the processreturns to step 865 s. If it is not OK, then in step 865 v the disk isjudged as being an illegal disk and the operation is stopped.

[0306] As described, since the circuit delay time TD of the reproductionapparatus is stored in the IC ROM, optical mark position information canbe obtained with increased accuracy. Furthermore, by setting thetolerance 866 and pass count for the software on each disk, the criteriafor pirated disk detection can be changed according to the actualcondition to allow for a scratch made on the disk after purchase. Thishas the effect of reducing the probability of a legitimate disk beingerroneously judged as an illegal disk.

[0307] As described in the above mode of embodiment, the piracyprevention method at the reflective layer level forms a physical mark inthe pre-pit area of the reflective film on the disk, instead of thepreviously practiced physical marking at the master disk level. Pirateddisk production can thus be prevented even if the disk is duplicated atthe master disk level.

[0308] In the above mode of embodiment, a new optical-disk recordingmeans was used that performs secondary recording on a two-disk laminatedoptical disk by using a laser. In the first step, physical marks wererandomly formed, and in the second step, the physical marks weremeasured with a measuring accuracy as high as 0.13 μm. In the thirdstep, their position information was encrypted and, using the secondaryrecording means, the encrypted information was recorded as a barcode onthe optical disk with an accuracy of several tens of microns which wasthe usual processing accuracy. In this way, optical mark positioninformation was obtained with an accuracy of, for example, 0.1 μm, muchhigher than the processing accuracy of a conventional apparatus. Sincesuch optical marks cannot be formed with the accuracy of 0.1 μm by usingcommercially available equipment, production of pirated disks can beprevented.

[0309] In the above mode of embodiment, the position information of theanti-piracy mark of the invention, which differs from one disk toanother, was used as a disk identifier. The position information and thedisk serial number, i.e., the disk ID, were combined together andencrypted with a digital signature; the thus encrypted information wasconverted into a barcode and written in overwriting fashion to theprescribed region of the pre-pit area, thus appending an unalterabledisk ID to each disk. Since each completed disk has a different ID, thepassword is also different. The password for one disk does not work onother disks. This enhances password security. Furthermore, using thesecondary recording technique of the invention, the password issecondary-recorded on the disk, permanently making the disk an operabledisk

[0310] The first-half part (I) has dealt mainly with one applicationmode of the barcode in which the barcode is used for a pirated-diskprevention method. In this case, as shown in FIG. 2, the barcode(stripes) 584 c-584 e are written over the prescribed region (stripearea) of the pre-pit area; therefore, the tracking is disturbed in thatprescribed region. If a marking 584 by laser light is formed in theprescribed region where the barcode, 584 c-584 e, is recorded, as shownin FIG. 2, it becomes difficult to accurately measure the address/clockposition of the marking. To avoid this problem, if, as shown in FIG. 39,the marking 941 is formed in a pit area 941 a at a radius positiondifferent from the radius position of the stripe area 923 a, theposition of the marking 941 can be measured stably with an accuracy ofone clock, as shown in FIG. 20(5). This has the effect of being able toidentify pirated disks more stably.

[0311] In this case, by forming a pinhole marking destroying only a fewtracks, as shown in FIG. 39, not only errors can be minimized but piracyprevention can be accomplished within the scope of the current standard.

[0312] Alternatively, the marking 941 may be recorded in the guard-bandarea 999 shown in FIG. 30. Since the guard-band area 999 contains nodata but address information, this has the effect of avoiding destroyingalready recorded data by recording the marking 941.

[0313] The optical disk of the invention has a structure such that areflective film is sandwiched directly or indirectly between two membersresistant to laser light and a marking is formed by laser on thereflective film. The above mode of embodiment has dealt with examples inwhich this structure is used for secondary recording of a barcode, etc.and a piracy prevention technique, but it will be appreciated that sucha structure may also be applied to other techniques. In the above modeof embodiment, the optical disk of the invention has been described asbeing fabricated by laminating two substrates with an adhesive layerinterposed therebetween. However, the adhesive layer may be omitted, orinstead, a member made of a different material, such as a protectivelayer, may be used; that is, any suitable structure may be used as longas the reflective film is sandwiched directly or indirectly between twomembers resistant to laser light. Furthermore, in the above mode ofembodiment, the optical disk of the invention has been described ascomprising substrates as the members that are laminated together, butother members such as protective layers may be used; that is, any memberthat has resistance to laser light may be used.

[0314] As described, according to the present invention, since an IDunique to each individual disk, for example, is converted into a barcodeand written in overwriting fashion to an ordinary pit area, both the pitdata and barcode data can be read by using the same optical pickup. Thishas the effect of simplifying the construction of the playbackapparatus, for example.

[0315] Furthermore, by barcoding the marking position information foruse as a disk-unique ID, the invention provides a greatly improvedpirated-disk and other illegal duplication prevention capability ascompared to the prior art. A piracy prevention technique of the priorart, for example, employed a method that deliberately arranged pits inserpentine fashion when making a disk mold. Such a prior art method isnot effective in piracy prevention, since a pirated disk can be easilymade by exactly replicating the mold shape from a legitimate opticaldisk. On the other hand, according to the present invention, since themarking is formed on the reflective film by a laser and its positioninformation is coded as a barcode, as described above, the contents ofthem cannot be made to coincide when making an illegal duplication. Theabove-described piracy prevention effect is thus accomplished

What is claimed is:
 1. An optical disk on which data is recorded withCLV, wherein, in a prescribed region of a pre-pit signal area on saiddisk, all or part of a barcode is written in overwriting fashion byselectively removing a reflective film in said prescribed region.
 2. Anoptical disk according to claim 1, wherein a control data area isprovided for holding therein physical feature information concerningsaid optical disk, and an identifier for indicating the presence orabsence of said barcode is recorded in said control data area.
 3. Anoptical disk according to claim 2, wherein a guard-band area where nodata is recorded is provided between said control data area and saidprescribed region of said pre-pit signal area.
 4. An optical diskaccording to claim 1, wherein said barcode is formed in such a mannerthat two or more barcode signals cannot occur within one prescribed timeslot.
 5. An optical disk according to claim 1, wherein said barcodecontains data at least including ID information uniquely given to saidoptical disk.
 6. An optical disk according to claim 5, wherein saidbarcode contains data including, in addition to said ID information, apublic key of a public key encryption function corresponding to said IDinformation, said public key being used when encrypting prescribed datafor transmission to an external party in order to obtain from saidexternal party a password required to reproduce said optical disk.
 7. Anoptical disk according to claim 5, wherein said ID information isencrypted or applied a digital signature to.
 8. An optical diskaccording to claim 7, wherein a secret key of a public key encryptionfunction is used when applying encryption or a digital signature to saidID information.
 9. An optical disk according to any one of claims 1 to8, wherein said optical disk is constructed from two disk-substrateslaminated together.
 10. An optical disk barcode forming method whereinpulsed laser light from a light source is made into a rectangular beampattern by using a rectangular mask and said rectangular beam pattern isfocused on a reflective film in a pre-pit signal region in a prescribedradius portion of an optical disk on which data is recorded, and at thesame time, said optical disk is rotated, thereby forming a plurality ofrectangular reflective-film-removed regions as a barcode in the sameradius portion on said reflective film.
 11. An optical disk barcodeforming method according to claim 10, wherein said optical disk includesa control data area for holding therein physical feature informationconcerning said optical disk, and an identifier for indicating thepresence or absence of said barcode is recorded in said control dataarea.
 12. An optical disk barcode forming method according to claim 11,wherein said barcode is formed in such a manner that two or more barcodesignals cannot occur within one prescribed time slot.
 13. An opticaldisk barcode forming method according to any one of claims 10 to 12,wherein said optical disk is constructed from two disk-substrateslaminated together.
 14. An optical disk reproduction apparatus whereinrecorded contents of a main data recording area, recorded by formingpits on an optical disk, are reproduced by using a rotational phasecontrol for a motor, while recorded contents of a different recordingarea than said main data recording area, recorded by selectively forminglow-reflectivity portions on a reflective film in said differentrecording area, are roproduced by using rotational speed control forsaid motor, and the recorded contents of said main data recording areaand the recorded contents of said different recording area are bothreproduced by using the same optical pickup.
 15. An optical diskreproduction apparatus according to claim
 14. wherein tracking controlis not performed in said different recording area.
 16. An optical diskreproduction apparatus according to claim 14, wherein tracking controlis, in effect, performed in said different recording area.
 17. Anoptical disk reproduction apparatus according to claim 16, wherein saidrotational speed is the rotational speed that would be achieved in saiddifferent recording area if said rotational phase control were applied.18. An optical disk reproduction apparatus according to claim 14,wherein the rotational speed of said motor in said rotational speedcontrol is maintained at a prescribed value based on a result obtainedby measuring a minimum-length pit in said different recording area. 19.An optical disk reproduction apparatus according to claim 14, whereinsaid low-reflectivity portions are a barcode formed by selectivelyremoving said reflective film.
 20. An optical disk reproductionapparatus according to claim 14, wherein said low-reflectivity portionsare a barcode, and when reproducing the recorded contents of saiddifferent recording area, a high-frequency-component signal generatedduring reproduction of said pits is reduced or eliminated by a low-passfilter, thereby making it possible to separate a signal which isreproduced from said barcode.
 21. An optical disk reproduction apparatusaccording to claim 14, wherein said low-reflectivity portions are abarcode, and when reproducing the recorded contents of said differentrecording area, the width of a signal obtained by reading said barcodeis increased to a prescribed width and then measured with samplingpulses from a control section.
 22. An optical disk reproductionapparatus according to any one of claims 14 to 21, wherein said opticaldisk is constructed from two disk-substrates laminated together.
 23. Anoptical disk reproduction apparatus according to claim 14, wherein saidoptical disk includes a control data area for holding therein physicalfeature information concerning said optical disk, and an identifier forindicating the presence or absence of said barcode is recorded in saidcontrol data area.
 24. An optical disk reproduction apparatus accordingto claim 23, wherein, after reading recorded contents of said controldata area and judging the presence or absence of said barcode, it isdetermined whether an optical pickup should be moved to an inner portionor an outer portion of said optical disk.
 25. A marking formingapparatus comprising: marking forming means for applying a marking on areflective film formed on a disk; marking position detecting means fordetecting a position of said marking; and position information writingmeans for converting at least said detected position information orinformation concerning said position information into a barcode, and forselectively removing said reflective film to write said barcode to anoptical disk on which data is recorded with CLV, wherein all or part ofsaid barcode is written in overwriting fashion to a prescribed region ofa pre-pit signal area on said optical disk.
 26. A marking formingapparatus according to claim 25, wherein said disk is constructed fromtwo disk-substrates laminated together.
 27. A marking forming meansaccording to claim 25, wherein said position information writing meansincludes encrypting means for encrypting at least said detected positioninformation or information concerning said position information, andwrites contents thus encrypted to said disk.
 28. A marking formingapparatus according to claim 25, wherein said position informationwriting means includes digital signature means for applying a digitalsignature to at least said detected position information or informationconcerning said position information, and the writing at least saiddetected position information or information concerning said positioninformation means writing information concerning a result of saiddigital signature application to said disk.
 29. A reproduction apparatuscomprising: position information reading means for reading positioninformation of a marking or information concerning said positioninformation, said position information or said information being formedby (1) applying a marking on a reflective film formed on a disk, (2)detecting position of the marking, (3) converting detected said positioninformation or said information into a barcode and (4) writing thebarcode with selectively removing said reflective film on said opticaldisk on which data is recorded with CLV; marking reading means forreading information concerning a physical position of said marking;comparing/judging means for performing comparison and judgement by usinga result of reading by said position information reading means and aresult of reading by said marking reading means; and reproducing meansfor reproducing data recorded on said optical disk in accordance with aresult of the comparison and judgement performed by saidcomparing/judging means, wherein all or part of said barcode is writtenin overwriting fashion to a prescribed region of a pre-pit signal areaon said optical disk.
 30. A reproduction apparatus according to claim29, wherein at least said detected position information or informationconcerning said position information is written to said disk by positioninformation writing means.
 31. A reproduction apparatus according toclaim 30, wherein said position information writing means includesencrypting means for encrypting at least said detected positioninformation or information concerning said position information, andsaid position information reading means includes decrypting meanscorresponding to said encrypting means, and by using said decryptingmeans, decrypts said encrypted position information or informationconcerning said position information.
 32. A reproduction apparatusaccording to claim 30, wherein said position information writing meansincludes digital signature means for applying a digital signature to atleast said detected position information or information concerning saidposition information, and writes information concerning a result of saiddigital signature application to said disk, and said positioninformation reading means includes. authenticating means correspondingto said digital signature means, and position information extractingmeans for obtaining said position information from an authenticationprocess performed by said authenticating means and/or from saidinformation concerning the result of said digital signature application,when an output indicating correctness of said authentication result isproduced from said authenticating means, said comparing/judging meansperforms the comparison and judgement by using the position informationobtained by said position information extracting means and the result ofreading by said marking reading means, and when said output indicatingcorrectness is not produced, the reproduction is not performed.
 33. Amethod of manufacturing a disk, comprising the steps of: forming atleast one disk; forming a reflective film to said formed disk; applyingat least one marking to said reflective film; detecting at least oneposition of said marking; and encrypting said detected positioninformation and writing said encrypted information onto said disk,wherein, when encrypting and writing, at least said encryptedinformation is converted into a barcode, and said barcode is written byselectively removing said reflective film on said disk on which data isrecorded with CLV, all or part of said barcode being written inoverwriting fashion to a prescribed region of a pre-pit signal area onsaid disk.
 34. A method of manufacturing a disk, comprising the stepsof: forming at least one disk; forming a reflective film to said formeddisk; applying at least one marking to said reflective film; detectingat least one position of said marking; and applying a digital signatureto said detected position information and writing onto said disk,wherein, when applying said digital signature and writing, at least aresult of said digital signature is converted into a barcode, and saidbarcode is written by selectively removing said reflective film on saiddisk on which data is recorded with CLV, all or part of said barcodebeing written in overwriting fashion to a prescribed region of a pre-pitsignal area on said disk.
 35. A disk wherein a marking is formed by alaser to a reflective film of said disk holding data written thereon, atleast position information of said marking or information concerningsaid position information is encrypted or applied a digital signature,at least said encrypted information or digital signature-appendedinformation is converted into a barcode, and said barcode is written byselectively removing said reflective film on said disk on which data isrecorded with CLV, all or part of said barcode being written inoverwriting fashion to a prescribed region of a pre-pit signal area onsaid disk.